Read user manual:
http://www.koduvalve.eu/files/FM5300.pdf
page 15
1 led - navigation led. blinks every 1 sec when device has GPS fix.
2 led - modem led. blinks on communication with modem. Device FW tries to initialize modem (you have no sim card) - so device is perpetually trying to initialize modem.
Thus communicating with it -> this led blinking.
Regards