This caught me out too, after claiming the code you have to go into the in game mailbox and claim the mail they send you which is when the keys are actually added. The trainer option then works correctly giving you a large number of keys.
Yes. This. Please. And "x2 Loot", "Plentiful Loot" as well. Honestly with as many options as this trainer has, a readme is really in order to explain how the game mechanics are being modified for more nebulous options like this. I would feel a lot better about enabling the options if I had some information as to what to expect.
I tried to experiment with the options but empirically consistent testing yielded inconsistent results and depending on the combination of these four options enabled, after disabling all options, the game's behavior changes again, but not to what it was before any of the options were enabled.
I am not complaining about any of the behavior mind you. This is all very standard trainer behavior. Just humbly requesting more information.
I came here to post about just this.
A little warning before I post, some of what I will post is descriptions of certain items that may be considered spoilers by some.
If this is a problem please let me know and I'll edit it or moderation can do so if they think it's warranted
So far I have only tested it with the skeleton key chest but the findings using that are as follows.
The "Increased Chance Rare Drops" option seems to only give items of Legendary(orange) type, and 4 of then seems to always be spells
The spells are always a variation of some kind of "twister" spell that has 2 different elements such as ice and fire, so the spell will do both ice and fire or whatever two elements it contains.
The "Super Rare Drops" which I would expect to be doing what I described above does not seem to do anything, either alone or in combination with the "Increased Chance Rare Drops".
Further testing may be needed in the field.
Something on your PC is likely interfering like AV/security/privacy/etc. No other reports of any issues and this is a big popular title.