VPN has stopped working in Mint 19

[SnuffGear]

After working fine for many months, my vpn has suddenly stopped working in 19. It still works fine when I reboot to Mint 17.2. Everything else, with regard to connecting to the internet, works properly. My vpn client is setup exactly the same on both 19 17.2.

I contacted the vendor, and after looking at my logs, they responded with the following,

"Apparently, from the log, something is specifically blocking UDP."

Any ideas?
Thanks

[SnuffGear]

iptables -L

Chain INPUT (policy ACCEPT)
target prot opt source destination

Chain FORWARD (policy ACCEPT)
target prot opt source destination

Chain OUTPUT (policy ACCEPT)
target prot opt source destination

[SnuffGear]

Update:
I have now discovered that my vpn connection works when I change from Mint 19 to Mint 17.2. I have both versions installed on the same hd. Didn't think to try this first. (it has been working for several months on Mint 19) Maybe some update has screwed with it?

Also, I can get the vpn to work in 19 if I change from UDP to TCP. Huh? (in 17.2 the connection remains/works in UDP)