I am trying to uninstall JMS MultiSites (version: 1.2.86) from a web site that we no longer plan to use as a master site.

When I uninstall MultiSites using Extensions Manager, the entire site (front-end and back-end) goes blank with the following error:



Fortunately, I was working from a copy of the site. I restored the site and tried uninstalling the patches first (from the "MultiSites > Check Patches" page). However, I got the same error:



What is the correct way to uninstall MultiSites without breaking the Joomla! site?

When you uninstall JMS, this restore the orginal files that you had when install JMS or the patches.
Something that is recommended to save is your latest "configuration.php" file in case where you would have change your DB connection (password).

Once uninstall, if you have a problem to run your website due you can try unzip an original joomla to ensure that all the file restore are the latest one of your joomla.

Thanks. I did figure out that it was restoring the original configuration.php, and that I needed to re-edit configuration.php to include changes made for the database.