In Flow Designer a wait-for-condition looks at a date. When this date is reached the flow should move forward. However it is stuck.
A wait-for-condition only updates when the source record receives an update. So for example, if the condition is state=closed, the flow will wait for that record to move to closed and then resolve the wait-for-condition. But if no update is received the flow cannot move.
This activity does not do regular checks on the source record. It only moved if the record moves so if you wait for a date to be reached it won't move forward unless the source record is updated.
The duration activity is designed to work with dates and times. Unlike wait-for-condition it can monitor a record and pick up on date/time changes without the record having been updated.