Google Calendar Sync problem

We have been using the plugin for a while with the google calendar syncing

1/ it is usually working but lately we are having troubles

any idea on how to fix the syncing (synchronize) problem ?

event on the google calendar is setup by user manually : on the website the time should not be available for booking…but it turns out the calendar on the site is not up to date….

2/ Also : we have a lot of google calendars, so it seems like we have reached the limit of calendars we can sync. I guess there is no workaround for that ?

thank you in advance for your help