Where are you starting them? Inside or out? My first thought would be they are too cold.

Are you still keeping them evenly warm and moist as you did the first time? Tomatoes normally germinate in the right conditions within a week. Al

Outside during the day and inside at night - they probably fluctuate anywhere between 65-90 degrees depending on the weather, the location and whether or not they are in the greenhouse or have covers on. On particularly chilly days/nights I either put them in my (very warm) laundry room or on a heat mat. They are either misted or watered every 2-3 days depending on how dry the soil has gotten. Never has soggy soil, never totally dry.

Seriously, I'm stumped. The seeds are the same seeds that I used for the previous flats that were destroyed so I'm reasonably sure that nothing was wrong with them... IDK. I think I may just give up and buy plants this year.

The cukes should germinate in a few days. I'm assuming that you covered the seeds with soil. Have you tried digging any of them up to see what the seeds look like? I would suspect that in order for NONE of them to germinate, you either cooked them, or something ate the seeds (mouse, bird)

Great illustration of reason #2,3,4 or 5 of why I germinate my seeds in baggies on paper towels. Easier to open up the baggie and look than to dig up seeds in starter mix to see what is going on.

I would guess that if you had them covered outside with plastic in the sun, then you probably cooked them. I have done that before in the greenhouse.