Offer pulled before planned start date - salvaging other roles?

Hi all, hope you're healthy and safe. I signed an offer letter back in February to formally start in mid-April. Just received word that the new company doesn't have the financial wherewithal to honor my employment in light of recent developments with COVID. Sucks for me, but trying not to wallow in self-pity - that's life.

However, I had gone through the process (2nd / 3rd rounds) with a few other firms that I know are 100% still recruiting, when not many firms are recruiting in today's climate. The problem is: I had already told the companies/headhunters earlier that I had accepted another role, and now I would have to go back to them with my tail between my legs. Is doing so a lost cause since I had already "turned them down" before and they know they weren't my top choice?

Any advice on how to re-approach old roles that you had turned down would be greatly appreciated.