If you want to try and troubleshoot plugin incompatibility you only need to look at the plugins which you have updated with new versions since the time you know your calendar was last working. I know it’s not easy to remember which you have updated recently but you can look at the plugin details to see the date of the last update. Many will be months ago.
You deactivate in turn and check your calendar page each time. If you find you have the calendar back then hurrah. You know that the problem was some sort of incompatibility between the calendar plugin and the plugin now deactivated so you can look at or contact both plugin’s support forums with this.
If you then worry that you have might have made something else go haywire with the plugin deactive it is possible to install an older version of a plugin so you could do that and reactivate.
Of course if it is the last update to the wp booking calendar plugin which has caused the problem then doing the stuff above won’t work. But I see that was last updated 4 weeks ago so presumably one of you will have updated it and had a working calendar for a while before this problem happened?