I see you referencing some sort of difficulty rating, but I don't see a setting for that on the android app outside of custom puzzles, so that's not a setting I changed. Suddenly I just have an 85+% success rate on puzzles and it won't give me difficult ones. Surely it's a bug
The setting is only available on web currently and should be available on the apps in the near future. However, the change does impact the apps
As Martin mentioned few comments above, this is not implemented yet in the App directly, so we have to "activate" it first through the Web so that it could work in the App (work around for now). Ive tested it yesterday, changed from Classic to Hard just to see if there will be any difference and i can confirm that the puzzles did get somewhat more harder or difficult.
Here is the direct Link:
https://www.chess.com/puzzles/rated
Or just go to the Web, in the upper left corner open the Menu and choose puzzles. When the puzzle window opens, change the difficulty and test it out for yourself 😊