Hi there Bo,
Thanks for getting in touch with us and sorry to hear about this issue 🙁
To recover the site, try downgrading to the last working version of the plugin → Downgrading a plugin to a past version
Once the site is back again, please test the update in a staging / development site and check the PHP error logs to see if there’s any evidence of the code generating the fatal error. Also, could you identify if it was The Events Calendar or Events Calendar PRO the one causing the issue?
Please let me know about it,
Best,
Nico