I am trying to use the Protool Control app with Sonar using the Eucon protocol. This works to a degree but has NO metering and is quite buggy. Not good for the Eucon protocol. Can anyone help please?

Ahh, Audiocon, what's the answer but better compatibility.

Sorry that doesn't help the OP but this is kindred to another thread. 😊 my apologies.

Joe_A
Ahh, Audiocon, what's the answer but better compatibility.

You my friend are hilarious! 

Sorry OP, I have to say I have never heard about such a protocol.
I currently use the Mackie MCU Pro.

EUCON Sonar plug-in is not open source and there was no changes in it since years. Unlike "old and stable" Mackie MIDI protocol, EUCON software get periodic updates. I guess CW has tested the plug-in with one particular device. Logically there can be many problems.
 
There are several Mackie emulators for iPad and Android, which are proved to work right with Sonar.