hi all, i gave all rounds of interview at oracle this feb, and when i mailed the hr regarding the feedback of the last round, she ghosted.

I made up my mind that i might have not get selected and got an offer from another company,
now i get a mail from hireright for my backgorund verfication for oracle, i did not get any confirmation of offer from hr or director, when i mail the hr regarding this, she does not respond and if i call the director, he does not pick it up.

I have my joining at the startup in early march, what should i do?
background verfication is done only once the candidate gets an offer right?
i don't understand what is happening here.

update: got an verbal confirmation of the offer.