Hi @adithideborah, the EngineStateValue may return as INVALID under scenarios where you have no connection or lost connection to interaction engine. Also if you ask straight away when the observer is created you might get an invalid value since the operations is asynchronous.
Are you accordingly experiencing frequent disconnection issue? If so, might be worth ensuring that all the Tobii software and firmware are fully up to date and that USB chipset drivers (and BIOS) are also updated. Failing that, a detailed specification of your system would be useful for further diagnosis.