Hello,
I am growing Rampicante for the first time. I'm very pleased with it so far!
Well, a couple of grown and the neck has grown, but where the bulb is, it turns yellow and withered. Is it SVB, improper pollination?, or disease?
Thank you for y'alls help.

Well, I don't know anything about that particular variety, but if it's like other squash, the female flowers have the fruit, and if they aren't cross-pollinated from a male flower (on the long stem), the fruit just withers and falls off.

I agree it is most likely an unpollinated female flower. If you have a male flower you can remove the stamen from the male flower and hand pollinate the female flower.

Thanks y’all!
I picked it and just cut off the end and used the rest for dinner. It was good!

A good thing about the rampicante is that it is a moschata variety, so it should be resistant to SVB. For the future female flowers, make sure you see a number of pollinators in all of the flowers; otherwise, hand pollinate them.

update:
I have pulled everything out of the garden to get ready for fall. The Rampicante was awesome!!!! It wasn't svb free, but I got a good harvest.
I will be saving seeds. It was vigorous, and seemed to "outgrow" the pest pressure. I call it a WIN!!!!