When performing an Endpoint search in ATP 2.2 and earlier, the search function was not searching all Endpoints.
The underlying database technology was not searching all Endpoints when a SEPM Group was specified. This has been patched in ATP version 2.3.
ATP 2.3 and later will search all Endpoints in the specified group as expected. If you are running ATP 2.2 or older and experiencing issues with the Endpoint search, please upgrade to ATP 2.3. or later.