Good morning Jagsare1,
What version of software is your unit/units currently running? They must have version 6.21 at least in order to upgrade to version 6.26. If your units do not have version 6.21 or higher you must first update the units to version 6.21 before proceeding to either version 6.23 or 6.26.
Some of the software updates are complete OS updates like version 6.21. Other updates are just application updates like version 6.23 and 6.26. It is recommended to follow the update instructions for each software load. The direction will indicate when a master reset is needed or other specific requirements before and after the software update process.
Kind Regards,
C-Bass