Please note that the current Quest tab display still uses the same total system that was previously there. It's just a different way to display it (separating out the Quests/Pursuits and the Bounties). You have a limit of 63 total items between both your Quests and your Bounties. You can see the current total amount at the bottom left of the screen when viewing them. While it may look like you still have space for Bounties, if you're at 63/63, then you'll not be able to collect more Bounties until you make room in either your Quests or your Bounties.