Whenever you see “An internal error has occurred while processing your request.” You should enable Debug and check the errors in the log file or the debug bar, never skip this important step of troubleshooting. If not in debug mode, detailed errors will not be shown (this is for protecting your site). Post the complete stack trace so that other users can discuss with sufficient information.
As suggested, you should also check HTTP response, which can show you a lot of information.
Press F12 and go the “Console” panel of your browser to check for JavaScript errors.
Inspect HTML in the “Elements” panel of your browser, check if the HTML for the uploaded images are outputted, or only URL not working, etc.
Check the upload folder of your project, make sure they are correct, don’t use "../". Also make sure you have granted write permission to the folder, otherwise, the script cannot create the folders or subfolders for the upload file. Check if the file are uploaded to the folder successfully first.
Test with normal .png images first, in case some image format may not be supported by PHP GD (assume you have installed GD properly, you may double check with phpinfo).
If you are a registered user of v2025, you may also send all your project files (including database and generated files) to support for testing. If your site is online, I suggest you demonstrate the error to them so they can check and test with the actual problem server.