As always, these 2 tricks:
#1-Always have a backup plan. Drive imaging is the bare minimum. Cloning and swapping drives is even better(so the old version and system drive don't get messed up).
#2-UN-Install the older version before installing the newer version of Pro Tools. Things used to work as an update, but moving to 2020, it seems best(or mandatory) to uninstall the old version first.
