Cannot access via OpenVPN with Bitdefender turned on

Until a few updates ago, it was no problem to access my admin page of my router from the outside via OpenVPN.

Now I get this error message in my browser when I try to access



This page does not work has not sent any data.


After disabling Bitdefender it is possible to access the admin page.

For the sake of completeness:

Hoping to fix this, I deleted Bitdefender Free completely. I tried a fresh install of Bitdefender Free. Immediately after installation, the access to the admin page did work even with virus protection turned on. Until then Bitdefender had not yet updated. Now that Bitdefender has updated, access to via OpenVPN no longer works.

Access to does work anytime in the local network (without OpenVPN). So it must have something to do with the combination of Bitdefender and OpenVPN, I guess.