Profile: Jennifer

Problem:
Existing created Layouts suddenly not displaying in backend wp-admin

Solution:
In general, the cause of such issue is conflict between third party plugins or theme or related settings.

You should try to resolve your issue by deactivating all third-party plugins as well as the default theme to check for any possible conflicts with any of the plugins or themes?

You can find proposed solution, in this case, with the following reply:
=> https://toolset.com/forums/topic/all-my-layouts-are-suddenly-gone/#post-616230

Relevant Documentation:
https://toolset.com/documentation/programmer-reference/debugging-sites-built-with-toolset/