In my case I realised that the issue was either a dependency or a permissions issue. I am running PHP Version 8.1.2-1ubuntu2.9 with EMR 7.0.0.0 patch 2. (Ubuntu 22.04.1 LTS)
My problem was that the Image Canvas field would not show the image. I followed the setup guidance given here: Using Image Canvas frustratingly it did not work.
The image data was going in to the database, but not loading into the editor and therefore impossible to draw on or save.
I concluded it must be a dependency in ‘Literally Canvas’ which depends on React.js. So I updated React.JS. I thought it was working, it seemed to momentarily.
I think it might be the version of node.js and needs to be installed with npm using NVM so that you cane set the version.
Rather than break my server I will build a test VM to experiment with this. If anyone knows the version of node.js that works with Literally Canvas that would be very useful.