Spice Jet Airlines — Booking through credit shell

Website:

Via.com

I had booked 2 Spicejet flights (RDP-BOM and BOM-RDP) for the months of March 2020 which were cancelled due to Covid outbreak. Through via.com, the booking was made and the amount was stored in credit shell. Now in December, 2020 i want the same booking with one passenger less but it is instructed that if I need to use the credit shell amount then I have to book the next flight through via.com only. I did the same but now via.com is not allowing to use the credit shell. I want the December booking to be made using the credit shell amount and via.com and spicejet is not allowing me to do so.