Users not automatically being added to Starling 2FA during registration

Hello, I am working on building out our workflows for Password Manager, and in initial testing, corporate registration for use with Starling 2FA was working perfectly - a user would register through PMUser and automatically be joined to Starling 2FA with their email address and phone number. For the past two weeks, I have not been able to get users to automatically join Starling 2FA upon registration.

I have attempted this with two different instances of Password Manager - 5.8.2 and 5.9.3 - and I have also unjoined and rejoined Starling in an attempt to kick start it into working. This one holdup is preventing us from being able to finish the project and go live. I am not sure where else to troubleshoot. I appreciate any assistance. Thanks.