UPDATE: Topology Mappings screen grab (host name obscured)
We have setup a new instance of SDL Web 8.5 with DXA v2.0 and the Model Service using the R2 data model.
Working Example (not accessible publicly) GET http://cis.building-blocks.com:8998/PageModel/tcm/5/index
When requesting a page model from the model service for our '400 Example Site' (tcm:0-5-1) we get the expected 200 response with JSON body.
Failing Example(s) (not accessible publicly) GET http://cis.building-blocks.com:8998/PageModel/tcm/6/index GET http://cis.building-blocks.com:8998/PageModel/tcm/7/index
However, after creating child website publications that inherit '400 Example Site' and publishing out the pages etc I get the following 404 Not Found response:
Whitelabel Error Page This application has no explicit mapping for /error, so you are seeing this as a fallback. Wed Jul 11 14:27:26 UTC 2018 There was an unexpected error (type=Not Found, status=404). Page not found
This applies to two test publications:
'500 Example Site (/en/us)' (tcm:0-6-1) '500 Example Site (/fr/ca)' (tcm:0-7-1)
Topology mappings have been registered in the normal way with a root web application of dxa.building-blocks.com and multiple child websites for /en/us and /fr/ca.
There are no errors being reported in the logs and we have confirmed that the pages are published in the broker and work for the DXA presentation application. Just seemingly not when interacting directly with the model service.