The test watchfc cannot be updated normally

That's not an error.  You'll see this message with an app you marked as beta when you first uploaded it to the store., telling you that only you can see or install it.  After you update it, it might not be updated for up to two hours on your garmin.

To make it public, you need to change the appId in manifest.xml and upload it it as a new app, where it can take a couple business days to be approved.

See https://developer.garmin.com/connect-iq/core-topics/beta-apps/

Server issue?

Did you change any of the text for your app between when it worked and stopped?   There are some things you can have in the description, etc, like emojis, that you can't use.  Maybe go back to just simple strings like "My test WF" and try that

Something else to check is the devices you have set in your manifest.xml, and make sure you don't include anything like "preview" devices, and only actual devices.

Sometimes you don't have to change anything, garmin change things (I don't think they know that they change or what they change sometimes, it's probably a side effect of other things)

There definitly is /has been a problem this weekend with the store.