If you can’t log into Black Propehcy, here are some solutions.
First of all go to Gamigo’s billing site and log in with your customer data. You can login here: https://billing.gamigogames.de.
Once you are logged into the billing system click on Community and then on Create. Select Blackprophecy from the dropdown and you created an account.
Next, don’t start Black Prophecy directly, you can find the Black Prophecy launcher in C:\Program Files (x86)\Black Prophecy Client\BIN\WIN32\launcher.exe
Let the Black Prophecy launcher update the game and click on Play. You should now be able to log in. If you are not able to log into the game, press ALT+tab on your keyboard and then make sure that your firewalls allows Black Prophecy to access the internet. It is safe to add BlackProphecy.exe, Launcher.exe and Patcher.exe to your firewall as trusted applications.
If you still can’t log into Black Prophecy, I suggest posting a bug report on the official forums.