I can no longer get my F5 VPN client to load despite the fact that it says it is installed properly

I had F5 VPN Client working perfectly on Safari 11 and it now will not connect. Asks to be installed each time and when manually installed says the installation was a success but I don't see the plugin in Safari and it doesn't function. All was fine under Safari 11 and no other changes on the MacBook Pro. Similarly, Citrix also doesn't work any more. Bummer!