Welcome, @Laurent_Schoenmakers,
Are you using the GCal integration that was just released in July?
Perhaps try removing and re-adding the integration. If you still have a problem try these troubleshooting steps, then please 1) report your problem by going to Report a Bug, clicking the New Topic button at the right, and following the instructions, or 2) contact support directly with these steps.
I updated this thread’s title to correct the misspelling to help in search as @anon91170507 pointed out. (Also, the warning Stephanie provided was not about the above GCal integration recently released but rather about the older version.)
Thanks,
Larry