I remember coming across a serious bug in a site that belonged to a top multi-billion company. My brother also found what essentially an unrestricted privacy leak (and possibly editing access) in a top university (leaked data is sensitive personal information, not academic). Neither of us reported (or exploited) what we found. Protection from this kind of blame-shifting and misdirected retaliation should be guarantee…
Maybe they could use some threatening instead of a proper report. Go to a public spot, open up a Tor browser, then report the vulnerability. Something like this: "I have hacked your system, accessed and modified , using . You have to send Bitcoins to , or I your database. Thank you for your attention." Maybe they will panic strongly enough to actually do something about the issue.
You have to fix the issue, or I your database.
Asking for extortion does not push them to fix their systems, only to pay you and/or find you.