I assume the reseller is just a reseller from another registrar, because I have never seen an official domain registrar that ran out of business, but I have seen so many resellers that take down their own business.
So, first you should find your official registrar, then contact them.
The official registrar of the reseller can be found on the domain whois.
The reseller website is also down and their customer care is also not responding.
It does not matter, normally.
As long as you are speaking about a gTLD, your important contact is the registrar. It is the one under contracts to perform its duties regarding your domain. He may have resellers, but at the end of the day, it is the registrar that is responsible ...