@alfredo It's most likely that you'll need to delete .minecraft/libraries/EMC/1.16.4/configs. Try deleting it and then restart the game, and see if the issue is fixed (by changing some things and restarting).
If that doesn't work, start Aristois up and then close it, and send your log file. See here how to send the log: https://discuss.aristois.net/topic/21/