Problems with the block section for prototyping

Hello! I’m prototyping a game in thunkable, but from one moment to another the blocks section turns out to be blank, when previously it was working without problems. It happens in any method of internet browser, chrome, Opera, Mozilla, etc.

The weirdest thing is that it only happens with this particular project. I have more projects created and in the others the blocks section appears without problem.

Excuse my bad English, it is not my native language. I hope you can help me.