Why doesn't my Pre Amp increase the volume?

It would not be the first time that such a board is shipped with different values than the documentation says. That said, it would be a no-brainer to check the resistor values, they seem clear on the picture, with a cheap meter.
With a magnifying glass (we all have one, right ? ;-) the code can be read off in 10 seconds.

KolfMAKER, that's the diy spirit!

Jan