F5 APM (failed to initialize local tunnel server)

I have seen this issue many times now and in my experience, I have almost always narrowed down the issue to be one of these 4 things blocking the connection:

1. Proxy Server
2. Network Firewall
3. Software Firewall
4. Corrupted Add-ons

Proxy Server: To check this, Disable any proxy and connect to Internet Directly and then connect to VPN. If the connection works after connecting to Internet directly, then allow the VPN IPs in the proxy server or allow it without requiring any authentication.

Network Firewall: Get the IT team to check if any network firewall is blocking the VPN connection. Firewall logs should show if the VPN connection was blocked. If this is found to be the reason, then add a firewall rule for the VPN IPs

Software Firewall: Windows Firewall or any other Software firewall can also block the VPN. many of the modern Antivirus softwares have inbuilt firewall. Some other software which intercept the network traffic like McAfee Intrusion Prevention can also block the VPN connection. To check this, disable all the software firewalls or any other software which intercepts and affects network traffic and then try. If this turns out to be the issue, then allow your VPN IPs through the software firewall.

Corrupted Add-ons: Sometimes, removing all the F5 components from the machine and then reinstalling them from fresh works. To do this, use the CTU (can be downloaded from APM welcome page). Remove all the components and then install them again.

Hope this helps.