What error do you see in the log under MC4WP > Other?
I don’t get any logs, I only get a log when I try to subscribe in the english version that this emailaddress is already subscribed. But when I do this the same for dutch, french, polish and german I don’t get any log.
How did you translate the forms?
If you are using WPML to create multiple forms in our free plugin and it’s not working I recommend contacting WPML support about that.
If you are using our Premium add-on that allows multiple forms I recommend to make a separate form for each language.