I unlocked 5th fragment slot but now when I logged in again Im back to only 4

I unlocked the 5th fragment slot before bed and got the confirmation on the fifth unlock but now when I logged in again next day Im back to only 4 slots and I dont have the quest displayed any longer on the quest tracker for witness t14 map bosses....

***Update:

Doing maven 10 boss invitation again doesnt solve it, still cant access fifth slot

I am also experiencing this issue. I have relogged and also ran another 10 maven witnesses and defeated the 10 boss fight again. Still no 5th slot

I believe this is a visual bug - I am in the same situation, but I haven't completed a nightmare map yet, which I believe is what gives the 5th sloth for me at least.

So maybe check what the 5 unlocks are, and see if you're missing one?