Is RW pin (5) grounded?
Have you tried adjusting the contrast pot?
The correct way to wire the contrast pot is to wire one end of the pot to ground and the wiper to pin 3. This actually makes adjusting contrast easier. The other end of the pot not connected or connected to the wiper. The long standing advice that the pot is wired to ground, Vcc and pin 3 is wrong. It is an error perpetuated over many years that begs correction.