I have the best luck with direct sowing - not fast but consistent. But if none of them are working for you is there any chance it is old seed or seed that may have been killed by heat and humidity?

If not, then my next best suggestion would be to try scoring or nicking the seed first - and then try the paper towel in the plastic bag approach. Scoring/nicking large seeds can often speed up germination as it makes it easier for the embryo to push it's way out.

Good luck.

Dave

Not sure how well this works on such a large seed... but you may want to try tossing the seeds in a glass of water to see if they are viable.

I believe the rule of thumb is if a seed floats it is non-viable as the hollow chamber causes it to float. Seeds that sink are still dense and (supposedly) viable.

I bought Yellow Crookneck squash last year (from Totally Tomatoes) and I tried to start them both in pots and in my heated germinator. They never sprouted. Not in the paper towel, either. I finally contacted the seed company and they sent me another pack which, surprisingly, sprouted just fine. I have no clue what happened to the first pack.
Kris