I had a total Gnome Shell extension crash recently - unfortunately my scheme of choice (Candy) I couldn't make out the main switch at the top of Tweaks to turn everything back on. I had a recent boot failure (my own fault for not disabling my Zorin drive). After installing 15.2 Core (Current version as at 5th March 2020) I wanted to add back some of the extensions i had before but some aren't compatible any more due to current version of Gnome Shell - just check your gnome extensions that you do have installed on the website, using the add-on in Firefox - if there are issues you will see an 'Error' message. - Search for that extension again, select it then click on red cross that appears next to error message to remove it so it doesn't clash with any other extension. I am currently in FerenOS so I can't upload an image at the moment.
