I'm testing v15 before rolling it out and I cannot get phones to provision. They provision just fine with v14. I use DHCP Option 66. I've also tried putting the server provisioning link directly into the phone through the phone's web interface. The phone shows up in 3CX and I assign it to an extension. But it refuses to provision. The event log shows nothing. I'm running on Windows Server 2012 R2 and I have 3CX fully updated. Test phone is Yealink T46G.