Did you make sure to add the proper shit to ShopAssistant for donor point store? Also, if Mandrith wont trade, go to ActionHandler.java, search "secondClickNpc" (or "secondClickNPC")
then make sure you add the case there.
for that it should look like (Numbers are examples)
case 123:
c.getPA().openShop(1);
break;
That might be incorrect since it's from the top of my head, but make sure something like that.