I came across this error on Fontself for Illustrator this week after an Illustrator update, and wanted to share the solution or fix I found just in case anyone else encounters this as well.
I started getting this error when trying to add glyphs:
(Something went wrong while creating your glyphs. Please select only Shapes, Compounds or Groups.)
To fix this, particularly on a Mac, go to Illustrator > Settings > Clipboard Handling…
You will get this Preferences pop-up.
Make sure that the Clipboard > On Copy: Include SVG Code checkbox is checked.
Magic! It’ll start working again.