How To Fix phpBB Error - The submitted form was invalid. Try submitting again.

Users, including forum admins, sometimes gets message while editing a post, sometimes for quick edits and sometimes for longer edits - “The submitted form was invalid. Try submitting again.”

This is not really an error but one of the two protection mechanisms in place in phpBB to protect your forum from spams. Here is how you can fix it.

Go to phpBB administration control panel and click on Post Settings. Now look for Limit editing time and Flood interval options.

The first setting is to limit the amount of editing time available for an user. A reasonable value is 120 (minutes).

The second setting is the minimum amount of time an user must wait between posting new messages. You can set it to something small like 10 seconds. However do not disable it as it is an useful spam protection.

Note: You can enable users to ignore this by altering their permissions.