If you can't add a new address to the whitelist, please make sure that the address is relevant for this cryptocurrency.
Then please confirm that the address is not a Segwit address. At the moment FMFW.io does not support Segwit addresses but this will be updated soon.
To add an address to the whitelist you have to confirm via clicking on the confirmation link we will send you via mail. Please note that the link only remains active for 10 minutes.
If you don't receive this confirmation email, please refer to this article.