Each if the boosts show that 69 are available, but none of them appear to be usable, boost menu claims they're inactive and pressing the button causes... nothing to happen.
Most easily recognizable when trying to use a one week time skip.
For example when trying to complete fame missions, since they gave a timer in which the mission would be completed at the current production speed and the suggestion to use a time skip.
Or when trying to use a lore boost to get books, the available boost number doesn't change and no books are given.
Sometimes the game offers me to buy a boost for gems instead, when trying to use a boost.
The money works if one is careful. You can keep upgrading after the cash hits 0, but the actual/another cash value keeps decreasing, causing one to be unable to buy new things or finish the level until you've earned enough cash to get out of the negative and as much as is required to buy/finish the level.