I sell on eleventh avenue as well and before March 2015 (when they were strictly groopdealz), I was getting completely paid off in 30 days. It's now June and I'm still waiting on payments from March AND I've emailed them multiple times many departments. Not happy either.
UPDATE: in January 2016 was apologized to and promised that things would get better as they have had a change of personnel. Asked me many times to list items, they told me specific items they wanted me to list, many of them were declined or they ask me to get more inventory, I purchased the inventory and those were declined, which made me extremely mad because I purchased more inventory just for their deal only for them to decline it anyway. Then of course my favorite, every deal they negotiate the price down 25% for either the item or shipping, if I don't fold, they decline the item even though most of those items have been listed before (many times they requested me to list the item again). The products that were accepted in January listed just fine, however, it's mid March 2016 and still haven't gotten payment from deals that ran in January 2016. They also change their reporting system, so now I cannot see the commission they took, they keep that hidden now and I have to approximate what it is and if it's wrong I can't do anything about it. I still have a few outstanding payments from 2015 that haven't been paid but no communication from groopdealz about it, including shipping payments. Still a terrible company. I don't know why I thought it would get better. I'd rather not sell then be out the money for inventory and shipping. They expect a lot from their sellers with nothing in return.