Using the demo version of 3CX, I'm trying to setup multiple Skype accounts with great trouble. I can get either one to register by setting one as a master, but never both. I hope somebody can help!
Your trying to use the same account multiple times. Use a different account for the second trunk. Or even better, don't use the Skype Gateway as it really isn't a supported product anymore.
They are different Skype accounts. In my opinion, the Skype Gateway is much more economical than Skype's VoIP service ($29/year/account for gateway vs $7/month/account VoIP), so I'd prefer to go that route.