invalid admin credentials. Check configuration

Trying to set up ZTNA using a firewall as a gateway with on premise AD as the identity provider. Regardless of the settings I use for the identity provider, the test comes back with this message every time:
invalid admin credentials. Check configuration

The troubleshooting documentation only says to check the settings. Is there any additional troubleshooting or information for this error that can be used to determine what the actual problem is?