Selling GC tips.
Giftcardgranny.com and
giftcardwiki.com are good aggregators for best rates. Be wary of selling on Ebay as buyer can put in a false claim that it was empty and you can get screwed.
Cardpool:
Verification: 415-419-8787 between the hours of 1230pm - 930pm ET. Have your order # ready.
Offers an extra 6% if taken in the form of amazon GC and will also pay quicker than a check.
If you haven't heard from them give them a call it may be stuck in verification. Large total value is a trigger.
GiftCardZen:
Will cancel the full sale if one of the GC are incorrect.
In general if an order gets cancelled, it's possible those gc are *tarnished* and you may have trouble unloading them. It is possible these sites communicate with each other in this regard as well. In this case you can do the PITA method of using the GC to buy/return items and get a new gc issue.