How can I fix the blue tooth volume on my Hitachi site radio?

I recently bought the new Hitachi site radio feom screw fix. Grwat radio, but when I connect my phone to it via bluetooth, I cam barely hear anything. It has only jiat started doing this, before it was fine I could hear the music on volume 10 no problem but now I turn it up to max and it sounds like its on volume 3. Any suggestions on how to fix this? Would I need to reset the radio, if so, how? Or is there another solution?
Any help would be appreciated