Hi!
Today I had this mistake:
The server cannot process the image. This can happen if the server is busy or does not have enough resources to complete the task. Uploading a smaller image may help. Suggested maximum size is 2560 pixels.
Actually, I had very small SVG image and plugin Safe SVG already installed, so size, I assumed is not a probleblem.
And find out that in my server is missing php-xml package.
So, I installed it:
sudo apt install php-xml
And it fixed the problem.