How can I find out why my Apple Cash balance is negative?

Apple Cash is a service that’s administered by Green Dot Bank. Contact an Apple Cash Specialist at Green Dot Bank by calling (877)-233-8552 

https://applecash.greendot.com/termsconditions/

What do the Apple Cash transactions show on your iPhone?

I sold 55,780 in crypto and was deposited into my wallet and it is gone now

My funds have been gone for 17 months now and apple has made no progress in recovering my funds