That dataref isn't writable by us, only X-Plane so there isn't anything we can do about that, that isn't a circuitous workaround.
Is this in regards to a third party add-on reading this dataref?
I think you've solved it, looked in the cycle_info.txt file and it said DEC 2021, despite me updating it through FMS data manger. ive manually updated it all will try later. i will let you know.
thanks
Change between hPa and inHg altimeter scales by using the DCP menu to navigate to config, then pressure. Lots of PFD and MFD options are available in these menus.