Hey guys, so sorry this is happening. We're going to provide a specific support destination shortly to provide help for this issue. Link here: https://support.runescape.com/hc/en-gb/articles/360018273338--04-Mar-Unable-to-access-the-game-UPDATE-

If you are seeing this error, the account is part of a very small number of accounts we referenced as likely being still unable to log in at this time - our team are continuing to work on anyone impacted by this to get you playing again as soon as we can, but this support form will make sure we are aware.