A blank page shouldn’t happen, but if you’ve lost your authenticator, you’ll need to use the recovery code you’ve saved. If the page is just blank that looks more like a cache or browser issue to me.
Update 2:
Anyone also having the issue, please contact support@lansweeper.com. They are aware of the issue and we’re working on fixing it ASAP.
Make sure you enable MFA for your account first! If you force MFA for the entire site without setting up your personal MFA, it will cause the issue.