No Firewall popup

I've got a client project that works fine in the editor, but once built, the resultant exe does not raise a popup asking for firewall access - and therefore can't connect to the remote server.

I've tried the build on 3 machines and none of them raise the firewall popup.
Using 2018.3.10f1 with ENet.

Any ideas why, or what I'm missing?

 

Sorted with thanks to the guys over at the ENet channel. Seems the latest mono required an update to ENet. All fixed now.