Anki back of basic card

I changed the template and now my cards dont work i would like to reverse the changes to basic

Caught exception:
Traceback (most recent call last):
File “aqt\”, line 87, in _on_closures_pending
File “aqt\”, line 59, in
File “aqt\”, line 76, in wrapped_done
File “aqt\”, line 798, in on_done
File “concurrent\”, line 432, in result
File “concurrent\”, line 388, in __get_result
File “concurrent\futures\”, line 57, in run
File “aqt\”, line 794, in save
File “anki\”, line 93, in save
File “anki\”, line 237, in update
File “anki\”, line 422, in add_or_update_notetype
File “anki\”, line 256, in _run_command
anki.rsbackend.InvalidInput: InvalidInput { info: “attempt to save stale notetype” }

You may need to restart Anki:

If you can reliably trigger that message in the latest Anki version, please let us know what steps you’re taking.