That is strange.
What version of The Events Calendar and Events Calendar PRO did you update from and can you still see all of the events in the admin screens?
Thanks also for trying some of the basic troubleshooting steps (deactivating all other plugins) … could I ask you to repeat that but also switch to a default, unmodified theme such as Twenty Twelve and see if that impacts on this?
Above and beyond that, if you could share your System Information as provided on the Events → Help admin screen that would be great.
Thanks!