1.)Uninstall Rotmg on Steam
2.)If you did that, reinstall it.
3.)Now you should be able to use your Replacer again with the current Hack Client.
4.)If that does not work, repeat steps 1 and 2.
Then you look that viedo.
Should work.
- - - Updated - - -
1.) Make sure you are using the latest client.
2.) If the problem persists, follow the instructions from the page.
https://realmstock.com/pages/client-errors