HR gone AWOL after clearing all rounds

I have cleared all rounds with one of the top consulting company and verified my documents on my holding offer too

The last call I had with HR was 2 days ago and she said she’ll close the final discussion for pay on the same day or latest by tomorrow (yesterday).

Now she has just stop responding my emails and messages and I’m holding an offer which is only valid till 1st December.

Any suggestions on what should I do?