It seems like you have old version of VC which does not works with latest version of wp .
Please update your wplms theme to latest version 3.8.5 .
If you are wplms version 3.6 or below then please follow :
Manually updating WPLMS : https://wplms.io/support/knowledge-base/manually-updating-wplms/
If you are at WPLMS version 3.7 or above then follow :
Auto updating WPLMS : https://wplms.io/support/knowledge-base/auto-updating-wplms/
After updating theme to latest version please follow this tip to update your visual composer to make it work with latest version wordpress :
https://wplms.io/support/knowledge-base/how-to-update-visual-composer/
after update please
disable Gutenberg editor on your WordPress site via WPBakery Page Builder Settings (in your WordPress Admin Dashboard).