As far as I can see there are no major issues with your event pages that prevent it from ranking. The main cause seems to be that there is simply a lot of competition out there. There are many sites that all describe the same event in more or less the same way. When I search for your example events, 'Poverty Bay Blues Brews Festival', the first page of results is filled with very similar sites / pages.
Try to make your page stand out of the rest by adding unique and relevant content to the event page that other pages don't have.
Also try to fix the schema markup errors you're getting. I see that with some of your events you don't include the time in the start and end date. I would advise using DateTime instead of just Date. See https://schema.org/DateTime.
Good luck!