Switching environments is always a process as you have configured your scripts to run with one OS, and now switching to another OS means the possibility of changes made "behind the scenes". For example Win 2012 R2 might display a window with a different handle than it does on Win 2016 or 2019, which means that if you have an step that focuses on that window, it will now fail.
When these types of migrations are done, we highly recommend keeping the old server up and running as long as possible. This gives you a chance to install the software to the new environment, export jobs from the old to the new, and test each and every workflow/task in the new environment. This allows your production to not be hindered by the need to edit jobs.