Events+ and MarketPress Integration

I have a problem in that when I add an event and select it as a paid event, the dropdown for the marketpress product does not populate. I have 2 products created in MarketPress - 1 for each event. The first event I created, the dropdown populated and I was able to select the product. When I create the second event, the dropdown does not populate. Both products have just one category 'Event' and the Events+ plugin settings are set to display products from just this one category.

The events are identical except for the date/time.

I tried deleting and recreating the Event category in MarketPress and removing and re-assigning the category to be used in the Events+ - still no joy.

Any ideas?