Weird.
Goto Helix Ultimate Settings -> Advanced -> SCSS -> Enable it -> Save -> Disable it -> Save
Try again in Joomla Clear Cache -> Delete All -> Clear Expired Cache.
If you have something like JCH Optimize also go there and press "Clean cache".
Goto SP Page Builder Pro -> Settings -> Purge Cached CSS -> Save Changes.
Check if "Frontend Editing" is there activated.
In your Browser deactivate all Add-ons -> goto privacy -> Manage data -> Search your Website -> Delete selected -> Close all Browser windows -> Open your Frontend Editor.
If nothing changes make a Video for the Support.