Hello, I just upgraded to a new mac and installed a fresh download of Thunderbird. Things are working well except for trouble subscribing to this astronomy calendar: https://cantonbecker.com/astronomy-calendar/astrocal.ics It works OK on my old mac/Thunderbird setup, but not on the new setup. Details: New system, where the astrocal calendar doesn't work: MacBook Air M4 2025, running MacOS Tahoe 26.1, Thunderbird 146.0 Old system, where the astrocal calendar works: MacBook Air Intel i5 2017, running MacOS High Sierra 10.13.6, Thunderbird 115.10.1 (64 bit) My steps to subscribe are Event and Tasks tab click Calendar On the bottom left I click New Calendar This opens a Create new Calendar window. Click On the network, Next I select "This location doesn't require credentials" and "Offline support" I fill in the URL: https://cantonbecker.com/astronomy-calendar/astrocal.ics, then click Find Calendars At this point on the new Thunderbird I get the error: Could not find calendars at this location. Please check your settings. (screenshot) But on the old Thunderbird I get that astrocal is available, and it actually works. Any ideas? Is it a bug in the latest version of Thunderbird? Thanks, Peter H. PS: The new mac's default Calendar app subscribes to the astrocal calendar OK. It's just the new Thunderbird that has trouble. PPS: The new Thunderbird does successfully subscribe to another calendar, of Japanese holidays https://ics.calendarlabs.com/54/44bd6152/Japan_Holidays.ics That makes me more confused as to where the problem lies.