Welcome,
There is no component ThunkableSwitch in App Inventor. It seems you have a very old aia that was made with the first version of Thunkable.
Yes, I have an old version, but I also need to open my project
I can't open the project. Help please says Unable to find component “ThunkableSwitch” while loading project “GyverString”
Sounds like the Project started life in Thunkable? It is not compatible with App Inventor.......
Provide the aia project here, maybe someone can fix it for you.
or
thunkable is still going, why not try it there: https://thunkable.com/
That is not the classic Thunkable, this is a complete rewrite. They are not compatible. The Thunkable Classic server shut down many years ago.