Pwc offered and ghosted!

So I received an offer from pwc, wherein before interview I had already disclosed 90 days notice period. Before release of offer HR said to try for early release, and gave tentative date of joining 30 days from release of offer.

As early release failed I emailed them to change DOJ but there is no response at all.

Is there a possibility that they ghost and revoke offer!

I already resigned 😂

One HR from bgv team does respond and asks me to keep following up.

But as I already resigned I want to be 100 percent sure that they are not ghosting me.

Unprofessional and unethical but what can I do!