There is no 24 volt power from the compressor back to sequencers. What may cause this?

Well,first the low voltage (24v) doesn`t run to or from the compressor it starts at the transformer in your airhandler/furnace that's where you need to start checking for low voltage . If you have an electric furnace / airhandler,you should check with a multi-meter for high voltage(220-230v) going into the transformer and 24-27 volts coming out. The low volts is sent to the tstat and the tstat then sends the signal to wherever it is set to run either heat or cooling. In cooling mode the tstat sends 24 v to the contactor in the outside condensing unit and closes the relay which sends the power to fan motor and the compressor,,

Hope this helps