My unit would display e001 and e003 errors. Cleaning the filter and replacing the ceramic ozone plate did not fix it. Ended up taking the board out and inspecting it. Three capacitors were bad. After replacing, the system is working again.
Most times the cover has an interlock. Look for something prijecting from cover and the a place where this would fit into. Align cover then close. If you dont see one then look under or behind filter. Also check the filter is installed correctly (direction of airflow). Remove power (unplug or circut breaker) then power back on might reset as well.