I was always able to Save selected task as template from File menu. Now that option is greyed out & not able to be clicked. How can I get that function back? Also, when I click Check for Updates, it shows "Couldn't find out what the latest version of Task Coach is". In "About" it shows Version 1.4.6, April 27, 2019
1.4.6 is the latest published version, though there is actually activity at https://github.com/taskcoach/taskcoach working to get it finally working with Python3 (and it is usable though has some issues and needs testing and isn't packaged for ready-to-go install)
I don't have that greyed out issue myself at 1.4.6 on Linux.
Maybe try temporarily renaming the .ini file while TC is closed so it starts fresh, see if it works again https://answers.launchpad.net/taskcoach/+faq/1061