Publishing past activities?

How do I reopen a past opportunity. Open a past opportunity. Past opportunity. Past event. Past workshop.

If an opportunity has already started, it is marked 'past'. In contrast to opportunities that are set to 'full', you can't just open a past opportunity again. The end date of the opportunity is in the past.

Changing the start date automatically opens the opportunity.

You can change the end date via Edit > Date and time (click on) > indicate an end date in the future.