A few days ago I was ablet o exchange five Tokyo Bonus Key: Silver for one Gold, now the swap shop won't let me exchange them, the counter stays at 0/5 and the items won't get highlighted in the menu even though five keys are shown, and the keys are not expired.

Your inventory is full

@Vashzaron Sure enough, thanks. Odd that there's no notification about inventory like other areas.

I'll add it is kinda odd its like that considering the new key could just take the space of an old one but it is what it is.