Ensure you have not set any IME Filter criteria that may be excluding some/all events from view (in IME > Event Monitoring > Basic View, click the Reset button (near the top-right) to clear the current Filter criteria, then press the Apply button to show relevant events). NOTE: By-default, the last 10 minutes worth of events will be shown. You may need to change this value then re-apply (for a sensor(s) where no event has occurred over the last 10 minutes).
Also, would be good to ensure that the clock on the IME host system _and_ sensors is accurate/correct.
Finally, what version of IME are you running?