[Hall of Famer]

Well it should work with the latest version of MyBB. I know one common cause of error is that people do not include a custom blank .htaccess in MyBB forum directory. This results in MyBB forum's url being redirected to Mysidia Adoptable's index page, causing problems like file not found error. This happens if you have MyBB forum as a sub-directory in your mysidia adoptables root folder, since by default all subdirectories in Mysidia Adoptables will be subject to its url-rewrite rule.

I am not sure if it applies to your issue, but you can give a try fixing it by uploading the .htaccess file in Mysidia Adoptables install folder to the forum folder. MyBB also comes with a .htaccess file, but its not in the correct format so it does not work. You can get it to work by changing it from htaccess.txt to .htaccess.

Also if you want to talk to me about this issue on AIM, all you have to do is to drop me an offline message. I will see it whenever I am available.