If you see this:
<msg data="27|dial|8004057119|2f4776f18ce7500b9b981466f3cbxxxx" />
Whenever you try to click to call, but your phone does not ring... then it is not the protocol handler but some configuration on the server side (could be lack of permissions to dial for the user).
If you do not see anything in the background page, then it could be the protocol handler.
So, if you are actually seeing a dial command attempted, you should then troubleshot on the server side, starting fop2_server in debug mode and looking whatever is logged after the dial command is received.
http://support.asternic.biz/?/selfhelp/view-article/how-to-debug-fop2/10
