Can we negotiate with a rejected offer?

You can always negotiate but have a damn good reason why you're accepting the offer now. Make up some shit about the meaning of life or something but has to sound thought through

No harm in trying.

Tell them you are ready to walk right through the door and start ASAP, instead of them spending that time to find someone as good as you and get going within the next week.

Saw this in Better Call Saul