My hvac blower motor works in heat mode only not cooling, will not work with manual mode either

Not knowing what brand unit you have it is either fan relay or the control board is bad

With the little information given, I would have to suspect either a bad fan motor or fan relay. The relay could be on a board or separate. Another possibility is a bad thermostat or thermostat wiring. The 'G' terminal on the stat & the wire between it and the furnace are the source of the control for the fan in cooling & manual fan. If 24 volts is not getting back to the 'G' terminal on the furnace the fan won't run in cooling or manual fan.