We are aware of a few solutions to fix this issue.
1. The most obvious one will be to check if the path to the content you are trying to access is correct. Sometimes, small typos on your browser will cause this error to appear.
2. Check for entries in the error logs related to this issue and check what's causing it.
3. If nothing is showing up within the error logs, make sure the permissions are correct. Chmod the folder to 755 and related files to 644. Clear the cache on your browser before trying again.
4. If you are using apache or Litespeed, create a backup of your .htaccess file, delete the contents, and check if the issue is fixed. Clear the cache on your browser before trying again. If it's fixed after doing this step, there's something wrong with your .htaccess file. You can try to reapply the parameters on your .htaccess - one by one to check what's the one causing the issue.
If you still require assistance after reading this article, please contact us.