As if by magic, my app started functioning again and no more of the aforementioned error..

Not a single comment by Apple yet...

We have the same issue, noticed that it becomes locked to a device after the issue occurs, once it happens it seems to get locked in a state of being unable to authenticate, something has clearly changed at apple since the release of 18.5 but my wife also has our app on her phone and she is on 18.5 I am on 26 BETA and we both have the same issue now albeit, she had it a few days before me. Followed your instructions above, I could not delete my device as its under a year since I added it so could only disable it, those steps did not work for me. At this point, we need Apple to step in now, several apps using Weatherkit all facing the same issue and not one of these threads has a developer/engineer response. I can't even test my own app anymore..

Good to know it isn't just me, system status shows an online reported status with no issues so hopefully it's recognised as an issue and resolve ASAP. The fact the issue stays device bound once it occurs is very worrying, will this just slowly begin to affect my userbase with no recourse for me? I really don't want to strip weather kit out of my codebase. its the backbone of the app but no idea what triggers or causes the issue to be device specific once the bug occurs in the first place.

Additionally, I wanted to share a peculiar, device-specific observation that may help diagnose the underlying issue: Persistent Failure State on a Single Device After the first occurrence of the JWT-generation error on a given device, even previously working builds (including the current production version) begin failing with the same WeatherKit JWT error on that device. In contrast, other devices that have never encountered this error continue to run those same builds without issue. Uninstalling the app from the “stuck” device does not clear the problem—subsequent reinstalls of builds that worked before still fail immediately. Steps Already Taken Rebuilt and reinstalled known-good versions on the affected device. Regenerated provisioning profiles and confirmed entitlements are correctly embedded. Rebooted the device, reset network/location/privacy settings, and signed out/in of Apple ID. Confirmed that other devices (same iOS version, same app binary) remain unaffected until they trigger the error the first time. Verified device date/time and network connectivity to Apple endpoints. Implication This behavior strongly suggests that once WeatherKit’s auth flow fails initially, some daemon or OS-level cache enters a bad state on that device, which persists across app reinstalls. It appears independent of the app binary itself (since older known-good builds also break), and is isolated to that device.