To make sure you have a fresh BoL installation please do the following steps.

1. If this is your first time using BoL or you want to make sure you have the proper prerequisites for it's use please http://sx-bol.eu/VC_RedistInstaller.exe.
2. Run 'Run me first as administrator' by right clicking on it and pressing 'Run as administrator'.

If you get 'Failed to login' after this
Open BoL Studio.exe and try to login (you will get failed to download on your first try)
Close BoL Studio.exe
Reopen BoL Studio.exe and try to login.

If you still get Failed to login after that change your password here http://forum.botoflegends.com/index.php?app=core&module=usercp&tab=core&area=email 
to only include only uppercase, lowercase and numbers.

Then request a HWID reset here http://forum.botoflegends.com/topic/46046-official-hwid-reset-topic/

-KorteX