after digging into some research I noticed that the one that I used to operate on is the classic app , how do I resume back to use the classic app? Is it block behind a paywall by any chance?
I wouldn’t bother with Classic Apps. Classic means old and expired. They will eventually go away.
If you were grandfathered in, I believe you can still create Classic Apps, and you can still modify existing Classic Apps, but they are being phased out and do not receive updates or support.