So this is what you get for not being a casher

Bit odd that they linked you to the STO Arc page. Just wondering, how many inventory slots do you currently have, and what were you trying to upgrade to? Also, have you used Inventory Stones in the past?

There are some glitches with some storage types where using a super stone does nothing if you've used regular stones before which is why they've retired the regular stones in the boutique. I can't remember if this affects the inventory or not.

As for them not helping you, they've been rarely known to reimburse players who face these storage glitches I believe. They've covered themselves in terms of upgrading the Pet Bag where it clearly says what will happen in the quest, but I don't think they've got a statement for Inventory or Safe slots.

Okay, I looked it up since it seems to be a similar issue to the Pet Bag, and before you hand in the quest it will state the following:

"WARNING: this will set your inventory to 80 slots, regardless of how many slots you already have. You will be able to increase it to 96 slots only with a third Super Inventory Stone. Are you sure you want to increase your inventory?"

So it seems like it's the same as the Pet Bag where the quest must be done twice in order to get the higher one or something like that. You did say you had 80 slots before, 80 slots now, and the quest you have is for 80 slots. Did you use Inv. Extension Stones to get your inventory to 80 before or Super Inventory Stones? Either way I don't know if you'd get reimbursed because they've put that statement in the quest itself which is basically notifying you that you'd need to use more than one Super Inventory Stone to upgrade to the next amount.

The super inv quest to get to 94 slots require you to have completed the super inv quest for 80 slots, not to actually have 80 slots. So even if you have 80 slots, without the quest completed for 80 slots via super inventory, it just wont count (not a smart design, I know) This problem appears when you do a mix of super inventory and regular inventory stones.
Seeing the screenshot I believe you have used one super inventory stone, just once, and regular inventory stones for another 16 slots. It is a very common people did it that way due to back when the inventory maximum slot amount first got increased, there was a code released shortly after with a pack that contain tradeable regular inv stones, making all servers flooded with cheap inventory stones.

It just continues to be a problem for people and we see this issue pop up regularly, but Im unaware of if anybody ever got reimbursed.

If you go to the inventory master now, the 80 slot quest is available there again?

Only thing I can think of then is that you did the 64 quest instead of 80 then. It says on screenshot the inventory was increased to 80, but it could be it just shows text of what u have rather than what the quest do. I dont know if the game behave that way and I dont have any way of testing it. Sadly there isnt any screenshot of the actual quest u took.

I would ask the GMs if they could look at your logs to see if it was the 64 quest or 80 quest you completed. If it was 80 quest you completed and its the 80 you can take again, then it truly is a bug and they should help you fix your character.

Oh and give them the link to this thread too else they would just ask you to go ask on forums.

What quest do you have available using regular stones?