I just tried and it worked fine for me. Make sure you have the correct site selected from the site menu before trying to log in
Bitvest temporarily blocks logins to an account/from an IP after a certain amount of login attempts (successful or not). wait a few minutes (like 10-30) before trying again. The more you try, the longer it blocks you.
If after a while it is still not working, please send me the dicebotlog.txt file from the bots's root folder to contact@seuntjie.com (or post it here if you want)