I had same problem today (20-aug-’20)
After updating 6 plugins and WordPress 5,5, the left menu was gone.
Updating Enfold with Update button -> didn’t work, no action at all
Updated Enfold via FTP (version 4.7.6) -> still NO left menu
Deactivated severall plugins -> no result (still the problem)
Using Chrome as browser in which the problem occurs.
Opened via Mozilla Firefox -> MENU works.
Opened in Chrome Incognito -> MENU works
Opening in Chrome (normal) -> problem occurs.

Pressed CTRL-F5 (refeshing disrecarding cache) in Chrome – > MENU works again.
Cache problem? Seems, but it solved the problem for now.
Hope this helps for other people, else let us know.