Like any software, sometime problems occur on Airbnb or even on Guesty's servers.
The first thing to do is making sure that you used the correct username and password, provided to you by Guesty.
If you still can't access your account, please to let us know (firstname.lastname@example.org) so we can try to troubleshoot the problem with you.
If the problem is on the Airbnb side our ability to help is a bit limited and a call to Airbnb support line might be required.
If we find the problem on our side we will fix it ASAP and have new credentials emailed to you immediately.