WordPress access denied

Hello,

I’m trying to access my WordPress account without success. I bought a new theme 2 weeks ago and go it install by your support team. I’m now trying to access both to continue the setup of my blog but it doesn’t work. Please see below the page that opened when I tried to log in :

Internal Server Error
The server encountered an internal error or misconfiguration and was unable to complete your request.
Please contact the server administrator, and inform them of the time the error occurred, and anything you might have done that may have caused the error.
More information about this error may be available in the server error log.

Can you assist me ?

Thank you