How to fix “The server cannot process the image. This can happen if the server is busy or does not have enough resources to complete the task…”

In my case, with a VPS managed with a cloud panel, I did the following:

1. Temporarily disabled the Cloudflare Proxy for the WordPress site.

2. Temporarily disabled the default WordPress image autoscaling on upload using the following filter:

add_filter( 'big_image_size_threshold', '__return_false' );

3. SSH-ed into VPS, installed the missing PHP extension called “ImageMagick” and reloaded PHP-FPM.

And the error disappeared, I successfully uploaded 6.6MB image-screenshot (2850×19720).