G&P ACOG problem

[Unseen21]

I own the above and have found that the horizontal adjustment does not appear to be working at all.
I have owned this for a while and it certainly did work when i first got it.
I did take a tumble once but the cross hairs didn't break. I took off the scope to try on another gun and then put it back on the original. Now it shoots to the right of the cross hairs. At 60 metres you cannot even see the BBs in the scope any more!!
So my questions are
1) Any idea what the problem is.
2) How can i fix it.
3) Since its not a real sight is there a repair guy out there who can help.

Regards