Hello, I tried to reproduce the error in my browser, but it worked fine. The calendar loaded without any issues. Have you tried loading the calendar in any other alternate browser to see if you get any error messages. If you get error messages in other browsers too, the problem may not be in your Firefox browser. But if it works properly in other browser, '''Try Firefox Safe Mode''' to see if the problem goes away. [[Troubleshoot Firefox issues using Safe Mode|Firefox Safe Mode]] is a troubleshooting mode that temporarily turns off hardware acceleration, resets some settings, and disables add-ons (extensions and themes). If Firefox is open, you can restart in Firefox Safe Mode from the Help menu: * Click the menu button [[Image:New Fx Menu]], click Help [[Image:Help-29]] and select ''Restart with Add-ons Disabled''. * Hold the '''Shift''' key when you open the Firefox desktop or Start menu shortcut. When the Firefox Safe Mode window appears, select "Start in Safe Mode".<br> [[Image:Safe Mode Fx 15 - Win]] '''''If the issue is not present in Firefox Safe Mode''''', your problem is probably caused by an extension, theme, or hardware acceleration. Please follow the steps in the [[Troubleshoot extensions, themes and hardware acceleration issues to solve common Firefox problems]] article to find the cause. ''To exit Firefox Safe Mode, just close Firefox and wait a few seconds before opening Firefox for normal use again.'' When you figure out what's causing your issues, please let us know. It might help others with the same problem.