Hi!
Thanks for bringing your issue to our attention. The various add-on plugins for The Events Calendar are dependent on using te same version due to changes that occur in the code base from release to release. You are getting the above message since your add-ons are on version 3.4 while The Events Calendar has been updated.
To resolve this issue you can download the last versions of both Events Calendar Pro and Facebook Events from our website. When logged into tri.be (forums count) you should see a menu item on top right called Account Central. If you go to the Download page you can download the latest versions for all plugins you’ve purchased and install on your site.
Please let me know if this resolves out your issues with the notification and Facebook Events not working.
Thanks again for reaching out to us.
– Matthew