MDLR
As per my reasoned guess, it is due to lack of trained pilots. There is hardly anyone in India who has flown RJ-70.
Obviously, the suppliers of the aircraft would have agreed to provide the pilots. The pilot may not have arrived.
Even if they have arrived, it is not a straight walk in to the cockpit. There are various sorts of clearances to be obtained including 'security clearances' in respect of expats.
Cheers
vgk1945