Intermittent Starting Problem.- Immobiliser Light Flashing

Hi,

My 2000 Mx5 (imported and fitted with aftermarket sterling Immobiliser), has gradually started to develop a starting problem. When I turn the key, occasionally nothing happens and Immobiliser light flashes. It doesn’t seem to make any noise or attempts to start. It seems to be getting worse and worse and takes longer to get it started. 

Does the Immobiliser fob have a battery that needs replacing? 

The Immobiliser waa fitted by import dealer in 2000

Cheers

Yes the fob does have battery.Replaced it and all will be fine, especially if its gradually getting worse!!Battery is getting lower etc

Thank you!

The fob seems sealed, do I just force it open?