Disabling AJAX solved the problem. I would like to know whether legacy templates will continue on WPLMS 4 or they will be deleted or discontinued in next releases.
I think these options belong to the legacy theme or some "legacy mode" I choose during installation (in the page where I can switch between WPLMS or Vibe pages):
https://i.imgur.com/LwvxJG0.jpg
Can you confirm that I will be able to keep using these options in upcoming versions of WPLMS?