Volvo V90 Forum : “why won,t"code"come back on radio.the battery was disscon. code was there but no...”

will have to take back to dealer to have it reprogramed,

Agreed.  It has probably gone into anti-theft shutdown mode.

When you disconnect the battery and reconnect it the radio theft system requires a four digit code.  Your local Volvo dealership/service has the database with all of the codes.  It goes by your VIN, if you attempt to enter the code and it is wrong you get three chances.  If you do not succeed you have to wait two hours for it to come back on and try again.