Fatal Error Will Not Let Me Do Anything

It seems you are using two plugins with the same functions:
the-events-calendar
events-calendar-pro

Delete one of them from the plugins folder.

If it has happened after recent upgrade or if you having Event Calendar Pro license contact their support directly

https://theeventscalendar.com/support/forums/topic/receiving-an-error-stating-fatal-error-cannot-redeclare-tribe_get_single_ical/

Igor,
Thanks for the tip, but since I cannot login (login page doesn’t even load), how can I access the plug-in folder and delete one of the plug-ins?

Login to your FTP and delete/rename one of the plugins from *wp-content/plugins* folder

Thanks for the quick reply, mbigul. I tried the FTP route right away. It manages to present the login prompt, but then the “Fatal Error” message pops up very quickly then disappears, replaced by the login prompt again.

I’m at a complete loss about how to gain access to the account and files. Any other tips?

Take a full site backup. Then rename the-events-calendar & events-calendar-pro folders from *wp-content/plugins* folder. Then check you can log in or not.

If you have Event Calendar Pro licence contact them directly. They can help you better.