If you disable a rule that runs on a schedule, then re-enable it in the future, it will never run. You must go into the date field of the schedule and set it to the current date which is completely unintuitive. It should continue to run again once enabled.

For example, my workflow did not run last night and I want to see why, I check the rule, the enabled checkbox is enabled.

So the only possible explanation is that it is waiting for a date in the past that will never come

This means it will never run ever again, once enabled