How to find reason for h1b visa revokation

My h1b visa is stamped 7 months back and I havent travelled to is yet. Last month my us employer told me that USCIS revoked my visa. But they are not ready to reveal the reason to me.

Is there any email id to contact uscis to enquire about this.?

Can i process h1b through another employer?

Do I jave to go to lottery process again?