Your question is not clear to me what exactly you're trying to do and what is your expected output.

For my understanding, you have upgraded your DXA web app from DXA 1.5 to DXA 1.8 with web-8.5 and your web app not getting downloaded your publish settings media system config files.

eg: \BinaryData\826\system\config_all.json

Try this below URL using postman to check /system/config/_all.json page binary content exist in broker DB or not?

http://domain:8081/client/v2/content.svc/BinaryContents(BinaryId=216112 ,PublicationId=826,VariantId='Y29uZmlnLWJvb3RzdHJhcA==')/$value

If this API call gets the response then no issue with broker DB, something wrong in your migrated DXA web application.

If this API call not getting the response then your _System->Publish Settings page not published to your broker DB.

Try unpublish and republish this page to check, enable your web app log file to TRACE to troubleshoot and keep it posted your findings and TRACE logs

Updated:

It seems to look like your CD Deployer is configured to store Binaries on the file system instead of in the CD Content Store (database).

Double check your broker-db for that binary content exists in the DB or not by running this select query in your broker db?

SELECT TOP 1 * FROM [BINARY_CONTENT] WHERE PUBLICATION_ID = 826 AND BINARY_ID=216112 AND VARIANT_ID = 'config-bootstrap'

if this query not getting the response then yes, binary stored in the filesystem, you need to adjust your content service cd_storage_config for binary.

<Storages>
        <Storage Class="com.tridion.storage.persistence.JPADAOFactory" Id="defaultdb" Type="persistence" dialect="MSSQL">
            <Pool CheckoutTimeout="120" IdleTimeout="120" MonitorInterval="60" Size="10" Type="jdbc"/>
            <DataSource Class="com.microsoft.sqlserver.jdbc.SQLServerDataSource">
                .......
            </DataSource>
        </Storage>
        <Storage Class="com.tridion.storage.filesystem.FSDAOFactory" Id="defaultFile" Type="filesystem" defaultFilesystem="false">
            <Root Path="/binary_folder_path"/>
        </Storage>
    </Storages>
</Global>
<ItemTypes cached="true" defaultStorageId="defaultdb">
    <Item cached="false" storageId="defaultFile" typeMapping="Binary"/>
</ItemTypes>

I hope it helps

Your question is not clear to me what exactly you're trying to do and what is your expected output.

For my understanding, you have upgraded your DXA web app from DXA 1.5 to DXA 1.8 with web-8.5 and your web app not getting downloaded your publish settings media system config files.

eg: \BinaryData\826\system\config_all.json

Try this below URL using postman to check /system/config/_all.json page binary content exist in broker DB or not?

http://domain:8081/client/v2/content.svc/BinaryContents(BinaryId=216112 ,PublicationId=826,VariantId='Y29uZmlnLWJvb3RzdHJhcA==')/$value

If this API call gets the response then no issue with broker DB, something wrong in your migrated DXA web application.

If this API call not getting the response then your _System->Publish Settings page not published to your broker DB.

Try unpublish and republish this page to check, enable your web app log file to TRACE to troubleshoot and keep it posted your findings and TRACE logs

Updated:

It seems to look like your CD Deployer is configured to store Binaries on the file system instead of in the CD Content Store (database).

Double check your broker-db for that binary content exists in the DB or not by running this select query in your broker db?

SELECT TOP 1 * FROM [BINARY_CONTENT] WHERE PUBLICATION_ID = 826 AND BINARY_ID=216112 AND VARIANT_ID = 'config-bootstrap'

I hope it helps

Your question is not clear to me what exactly you're trying to do and what is your expected output.

For my understanding, you have upgraded your DXA web app from DXA 1.5 to DXA 1.8 with web-8.5 and your web app not getting downloaded your publish settings media system config files.

eg: \BinaryData\826\system\config_all.json

Try this below URL using postman to check /system/config/_all.json page binary content exist in broker DB or not?

http://domain:8081/client/v2/content.svc/BinaryContents(BinaryId=216112 ,PublicationId=826,VariantId='Y29uZmlnLWJvb3RzdHJhcA==')/$value

If this API call gets the response then no issue with broker DB, something wrong in your migrated DXA web application.

If this API call not getting the response then your _System->Publish Settings page not published to your broker DB.

Try unpublish and republish this page to check, enable your web app log file to TRACE to troubleshoot and keep it posted your findings and TRACE logs

I hope it helps

Your question is not clear to me what exactly you're trying to do and what is your expected output.

For my understanding, you have upgraded your DXA web app from DXA 1.5 to DXA 1.8 with web-8.5 and your web app not getting downloaded your publish settings media system config files.

eg: \BinaryData\826\system\config_all.json

Try this below URL using postman to check /system/config/_all.json page binary content exist in broker DB or not?

http://domain:8081/client/v2/content.svc/BinaryContents(BinaryId=216112 ,PublicationId=826,VariantId='Y29uZmlnLWJvb3RzdHJhcA==')/$value

If this API call gets the response then no issue with broker DB, something wrong in your migrated DXA web application.

If this API call not getting the response then your _System->Publish Settings page not published to your broker DB.

Try unpublish and republish this page to check, enable your web app log file to TRACE to troubleshoot and keep it posted your findings and TRACE logs

Updated:

It seems to look like your CD Deployer is configured to store Binaries on the file system instead of in the CD Content Store (database).

Double check your broker-db for that binary content exists in the DB or not by running this select query in your broker db?

SELECT TOP 1 * FROM [BINARY_CONTENT] WHERE PUBLICATION_ID = 826 AND BINARY_ID=216112 AND VARIANT_ID = 'config-bootstrap'

if this query not getting the response then yes, binary stored in the filesystem, you need to adjust your content service cd_storage_config for binary.

<Storages>
        <Storage Class="com.tridion.storage.persistence.JPADAOFactory" Id="defaultdb" Type="persistence" dialect="MSSQL">
            <Pool CheckoutTimeout="120" IdleTimeout="120" MonitorInterval="60" Size="10" Type="jdbc"/>
            <DataSource Class="com.microsoft.sqlserver.jdbc.SQLServerDataSource">
                .......
            </DataSource>
        </Storage>
        <Storage Class="com.tridion.storage.filesystem.FSDAOFactory" Id="defaultFile" Type="filesystem" defaultFilesystem="false">
            <Root Path="/binary_folder_path"/>
        </Storage>
    </Storages>
</Global>
<ItemTypes cached="true" defaultStorageId="defaultdb">
    <Item cached="false" storageId="defaultFile" typeMapping="Binary"/>
</ItemTypes>

I hope it helps