@n8lbv
The issue is probably the '5' thing you mentioned.
Dono what that is.
Look here : https://www.pfsense.org/download/
The next important thing is that OpenVPN itself - see here : https://openvpn.net/community-downloads/ went from the 2.4.x series (th ese are NOT pfSense series numbers !!) to the 2.5.1, 2 or 3 version.
And between2.4.x and 2.5.x (OpenVPN !) things changed, some parameters are faced out, some can even do other things. Mixing 2.4.x settings (opvn file) with 2.5.x (2.5.2 is the OpenVPN version on pfSense 2.5.2) can crate issues. The other way around : same thing.
So, using pfSense 2.5.2, things changed.
I'm using a OpenVPN 2.5.x client on the client side, and pfSense 2.5.2, this works just fine.
And yes, I to go to the OpenVPN 2.5.x release info page ( again : here https://openvpn.net/community-downloads/ ) and read the "Overview of changes since OpenVPN 2.4" part.