To rule out that the issue is caused by access what I've done is created an empty "plugins" folder and rename the existing plugins folder to "plugins-current" - that means all plugins will be automatically deactivated and it will not have any effect.
Then I also try to set the default value for the key "toolset-access-options" available at "wp_options" table but still its not working. It looks like your database is corrupted and I do not have any solution to offer you. Because with empty plugins folder still its not showing the plugins page etc..etc..
If you have any server-side cache or plugins install please remove that as well.
I do not have any server-side cache or plugins installed, so I do not know what to do. I have database backups of the site before this issue happened so I will try them. It definitely happened as soon as I saved the Toolset Access control settings. This is why I am asking if Toolset Access writes and amends other files in the WP ecosystem.
Toolset Access do not override the core files but save the related settings in database but as soon as you remove the plugins directory (due to that all plugins should be rule out as it will be automatically deactivated) and I checked there is no difference.
I strongly suggest you to try old backup I think that will be the best option for now and help you to resolve your issue quickly.
I have just tried to create a test site on Local by Flywheel and uploaded the database, theme and plugins from 23/6/2019 (day before issue) through updraft plus. All was going well but when I went to view the site this is what I got. Please click link to view.
hidden link
There appears to be lots of issues around Toolset Types. Does this explain anything?
I uploaded a database backed up from 20/6/2019 and it is now working. However, the Toolset Access plugin has been deleted so should I download a new version?
Yes - you should download the latest version of Toolset Access plugin fro your accounts download page and install it.
=> https://toolset.com/account/downloads/
