It seems that with every update 343 does Halo 5, there’s always a few glitches in them. Currently, when I open a req pack I have to sell valuable reqs to sell the ones that I don’t want. When going through my collection, I try to sell duplicates of some reqs but then the “Sell Error” pops up. 343 need to fix this as soon as possible cause it’s really frustrating trying to sell reqs before a game starts and the sale takes too long.
you can sell multiple reqs on halo waypoint. you will need a chrome extension in which you can find and install pretty easily. its called waypoint tools. give it a try but if you keep on selling on the game, either it takes long to sell each one of then and at a point you will start getting errors. give it a try.