Hi Mar,
Thanks for reaching out, and sorry to hear about the issues you are having 🙁
It seems you are calling the class ‘TribeEvents‘ which name has changed to ‘Tribe__Events__Main‘, Can you search for uses of ‘TribeEvents‘ in your functions.php file -located at wp-content/themes/your_theme/- and change those to ‘Tribe__Events__Main‘?
If you can check if the error is still present with default Tweentyfifteen theme, that would be great!
Please let me know if you can manage to find the old class call,
Best,
Nico