Standard stuff:
do you see link light on both interfaces PC's are plugged into? Does show interface terse show those interfaces are up? Perform show ethernet-switching table and do you see the PC MAC addresses showing up and associated with proper interface?
You could also configure a VLAN with these interfaces in it, add some L3 address to the VLAN, and then see if each PC can ping that IP - which would be IP associated with Master RE. To check other switch, perform a Master switchover.