tunnel failed after antivirus avg from trial to full protection

On the Windows edge client, tunnelserver is the process that handles comms between winsock and the VPN network driver. It implements TLS/SSL, F5 FastPPP, PPP, LCP, iSession, and a few other things and serves as the primary "TCP to PPP proxy". This allows the F5 VPN driver to be much simpler (more secure) because it doesn't have to do much besides just talk PPP and FastPPP.

In a who-talk-to-whom diagram, it might look something like this:  

Network -> Windows -> Winsock -> Tunnelserver -> F5 VPN NDIS Driver -> Windows Network

From a tech support perspective, tunnelserver does a lot of stuff. It has OpenSSL in it and does a lot of network stuff so it is sometimes terminated or prevented from operation by antimalware / antivirus software, or firewall software. You can typically add processes and executable files to an "allow list" in AV software, so make sure you've done that.

This is an example of the kind of thing that happens with interop against some AV software vendors:
https://my.f5.com/manage/s/article/K10893