I am having the same problem. I run both Desktop 2019 and Desktop Pro Plus 2022 on different machines. And office 365 on Windows 11. The Create customer letters no longer opens word. I attempted to contact support and was just told they are working on it, with no time-able as to when it will be fixed.  I can export to an excel file and then manually do a mail merge, but it is really ackward and not a good solution. Anyone have any fixes for this?