Error getting token from Google when checking Google Play Integrity on Pixel 6 with CalyxOS

Describe the bug
After installing the new version of CalyxOS with microG 6.3.0, I tried the Play Integrity API Checker app, which just gives the error "Error getting token from Google: Unknown internal error." I do not have an unlocked bootloader and Magisk is not installed either.

This isn't much information, but I don't know how to get more from the app. If anyone knows how to check easier what the actual issue is, please let me know and I will provide more info.

The specific app I'm using is https://play.google.com/store/apps/details?id=gr.nikolasspyr.integritycheck&hl=en_GB but no apps I've used that require play integrity work either.

In microG's Google SafetyNet page, there no apps listed that are using SafetyNet, despite the fact that I have multiple apps which do use Play Integrity.

Screenshots

System
Android Version: 15
Custom ROM: CalyxOS 6.3.0
microG version: 0.3.6.244735-27 (e7e4dbc)

Please let me know how to get more information about the specific issue.

No repository file, test, or code entry point is identified in the report. Start by reproducing the failure with Play Integrity API Checker on Android 15, CalyxOS 6.3.0, and microG 0.3.6.244735-27, then gather the missing error details and trace the Play Integrity request. Done means identifying the cause of the token error and confirming that Play Integrity apps work without the reported failure.