Lightning is no longer displaying any data from my main calendar. Lightning is installed and working ( Tbird V 52.9.1, Windows 10), and it displays my additional gmail calendar OK, but my Lightning calendar data has vanished overnight. When I check 'Tasks & Events' in Thunderbird, the missing calendar is ticked, but is shaded gray. I have found the calendar .ics file on my PC, but I cannot get it to display in Lightning.
Any suggestions welcome.