What power supply are you using and how is it connected to the board. I had to increase the size of the picture you posted to see the connections but it is not very clear. A similar board I have which is for a 3255 amp needs a split rail supply + OV - not just +/-
One of the connectors on the board has 3 pins and is probably for a split rail supply.
One of the connectors on the board has 3 pins and is probably for a split rail supply.
EDIT: I have looked at the board on Aliexpress and it is only a single power supply +/-