6.x client for Windows will no longer place calls - Call could not be created

[JCrabtree911]

We have a working configuration for 5.2.6 that lets us place calls to our SBC and SIP proxies. If we upgrade from 5.2.6 to any of the 6.x clients then attempt to make a call, Linphone immediately reports "Call could not be created" before sending so much as a single packet of data.

[dalecosp]

Me too! v6.1.0 - "Error - call could not be created". Reverted to 5.3.2, normal operation.

Collected zero logs on 6.1.0, which could be PEBKAC.

System is Windows 11 24H2 build 26100.7840