Flashing "Play Offline"/"Play" - can only play offline Java

For the last 9 hours the launcher has kept flashing offline and online and logs show a 403 error on https://api.minecraftservices.com/entitlements/license

Offline mode MC Java launches just fine but I can't play on Realms after this started happening (getting this issue: MC-252942)

20 hours ago it was fine. Might have been the previous version, not sure.

I purchased the Java version roughly 11 years ago and have since migrated to a Microsoft account.