Cruising solo

Hey all! So I booked a cruise in December for this upcoming March for two people thinking that I would be able to find someone to go with me. The cruise is now in less than 25 days and no one can go with me. My question is when it comes to check-in what is that gonna look like? Should I let Carnival know that I’m going solo ?Will I be getting any money back from Carnival?

Also, has anyone else cruised solo and can give me some advice?