June 2018
This is how I get the prompt to sell heirlooms:
1) click on the "store" button at the top of your screen (supposed to be a shopping bag butooks like a lock to me)
2) click on the heirloom store tab (the last one on the right for me)
3) click on the heirloom collection near the upper right
4)click on any heirloom with a little green number in it's corner and you will be asked if you want to sell it.