Okay, so you’ve lost access to your App. That wasn’t clear to me, which is why I asked.
So to be clear - you can sign into the Glide Builder, but your App is no longer there - is that correct?
Was it a Classic App by any chance?
If it was, then that would explain why it is gone. Support for Classic Apps was removed more than 2 years ago, and they were fully deprecated at the end of June this year. Glide made multiple announcements about this over the past few years, the most recent one below: