"Bitfinex" already gives you some solution you should following the instructions.

If you're not from the "Cuba" but you have an activity traveling to cuba and you doing some activity login to your bitfinex account you should give them an explanation about your case regarding the activity of your account.

IMO, if you don't have any activity on cuba you should contact them first by option 1 before sending any document to them. Maybe you can get another solution about your problem from them.