09-14-2022 Hi Gordon,did you try the following steps?1. go to the "phone security configuration" in non-working  ATA190 and change transport setting from "TCP+UDP" or "UDP" to TCP only, this will force the ATA 190 to use TCP for CUCM communications. ...

Hi Gordon,i have test some cases with the ATA. If i disabel the mixedmode in the Callmanager the ATA will register.Kind RegadsSven