Your posted voltages are as expected*
The reverb bricks have internal capacitors on the input and outputs, so these will sit at whatever voltage you connect them to. V+ should be 5V and the 2 grounds at 0V.
*For what it's worth, the circuit in the schematic would benefit from a number of major tweaks and/or a significant redesign. Unless it is supposed to sound like sh1t, there should be a capacitor on the output of U1, which is probably why you are having problems. As drawn, it should pass dry signal, but reverb will be quiet and/or distorted.
*assuming you have a cheap DMM.