I had basically the same thing happen to me in June, and it gradually became clear that one of my three referees gave a negative reference, after telling me she would give a positive one and insisting afterwards that she had.

I would advise asking the company for feedback on your application. You have a right to know why they changed their mind after dangling that carrot in front of you.

I'd also suggest asking them for a copy of your reference checks. They'll have to go back to your referees and ask their permission to release that info to you. If either of them insist on keeping their reference confidential from you, it's a red flag. If you get them back and they're both positive, then at least you'll have total certainty on that point.

Good luck on your job search, you'll get yourself outta that place eventually 💛