* Clients site ( this is the site that hosts a client request list)
* Opportunities site ( this is a subsite of the clients site and had a list call opportunity)
A content type has been created at the root site collection called opportunity. I beleive that in general content types should be created at the root site collection level so that they can be reused.
The opportunity list uses the content type opportunity and all fields from the content type come across as expected.I now need a lookup within the opportunity list using the clients list as a source for my values. I can't create the lookup on the opportunities list itself as the client list lives wihtin a different site. I can't create this lookup at the root site collection either for the same reason.
So the lookup field has to be created at the clients site and then be included in the SharePoint clients list. Within SharePoint this all works as expected bu not in PowerApps.