I have a bryant furnace.and the pilot comes on but the gas blower will not kick in. The furnace blower will come on.

Exact model number?

Exact model number?

It it a Bryant Plus 90. Model 398aaw048080D,

I believe your unit is around 19 years old and I doi not have any information in my records for that unit.

I would start by checking the small draft inducer blower motor to see if it is good. If it checks good then the circuit board is suspect.