ThunderbirdPortable and Lightning Calendar on Win7/10
I have been having problems with portability of Thunderbird 60.0 (Portable edition 2.1.2.0 from 8/6/2018) installed on a USB2.0 stick between Windows 7 and Windows 10 and Lightning Calendar not always available.
Initial search for this problem led me to 'Calendar update Issues with Thunderbird' at https://support.mozilla.org/en-US/kb/calendar-updates-issues-thunderbird