How to activate both SIMs on Dual SIM, Android Phone?

I have an iNote Mini (Dual SIM)
Android Version 2.3.5
Software Version 6820_2.3.5_c913A_it1350_v11

Can't activate SIM2, only one SIM is active, both are inserted correctly.

When I go to Phone Settings;
There is no SIM Management, instead, there is "Dual SIM Settings",
Under this, Standby SIM card setting,
Under this, icons for both SIMs, but only SIM1 can be ticked,
SIM2 is grayed out.

Will appreciate any help.

Thanks.