For the past few times I've held the battlefield portal, including now (about half an hour before 00:00), I haven't been able to trade for items. Even when I check frequently to see if I have enough of the specific material, the "trade" button doen't show at all. I'm not sure if this has something to do with energy either, as the squads never had full points when I attempted to trade.

Is this happening for a reason?

Edit: Yes, I did make sure I was on the correct squad's page.

Please make sure that you have the correct squad active when you attempt to trade. The button will appear only when the squad on the portal is selected. 

(Bump)

Are you sure you have an empty space in your warehouse?

I normally don't, so that just might be it. I'll check to see next time.

We checked this issue with your user data when you reported it, and we didn't find any problems. Could you please make a screenshot?

I'll be sure to the next time this happens.

Thanks for the help as well!

I just had the same thing happen after making my way to the portal so the exchange wouldnt be wasted. I refreshed, went to other squads and back, switched moon options, restarted browser and tried another device (tablet). Had I not gone here and seen what arete said I would have assumed the portal to be horribly bugged and given up my position. 

The exchange text does not warn you that you have no space, it simply looks as if you arnt even on the portal and can not accept it period. 

Here's what it looks like along with proof that I have enough of the requested material. RIP my portal position in any second now lol, atleast the item didnt get wasted by someone who didnt have quartz. 

I apologize for the blurryness, I had to zoom the screen out to capture the entirty of the battlefield and trade box. 

This is weird, Mon, because you probably have one of everything you can get from the portal and space to spare, so there goes my theory...

It did give me a repeat item too, there was already a spot reserved for that item to drop into.

But I don't the top stable/warehouse teir blueprints, so in theory I would of needed a space open incase it was one of those. 

It's weird all around..

Thank you so much for investigating this case!  We added the warning about inventory space.

There always must be one empty slot even if you end with a copy of item which you already have. It's it unknown which item you get until you actually get it.