It might be something that we need to fix on our end to prevent it from coming back, but you could also try deleting the config file for an immediate fix (however this would reset all of your other settings as well)
aristois doesn't support 1.21.4 forge it only supports 1.8.9 / 1.12.2 / 1.16.5 / 1.17.1 / 1.18.2 / 1.19.2-4 / 1.20 / 1.20.1 for forge version however you can use fabric instead of forge for using the latest version of aristois