The plugin needs to read the API for all events every time the cache frequency is run. If you have hundreds of events this can take a while.
Some cheaper shared hosts have a PHP timeout limit of 30 seconds. If this is not enough time to read all your events you may get ‘No Events’ at all. £0 seconds should be enough for 50 or so Events.
If you are having issues with lots of events then you may need your host to increase your settings which may require an upgrade in your hosting plan.