There are few other plugins installed. However, NameCheap support team disabled all other plugins and used the default theme. The issue continues to exist.
Moreover, “GD bbPress Attachments” plugin was tested using another domain with a fresh WordPress installation (version 5.5.1) with only one plugin i.e. BuddyPress version 6.2.0 the same issue continues to exist.
It seems that “GD bbPress Attachments” might be not compatible with the new version of WordPress/ BuddyPress.
Should you require more information please let me know.