Update UhcCore to its latest version (1.18.1) that provides support for 1.16.
https://www.spigotmc.org/resources/uhccore-automated-uhc-for-minecraft-1-8-8-1-16.47572/updates
update orebfuscator to this forked version https://github.com/TeamWuffy/Orebfuscator
(current version https://github.com/lishid/Orebfuscator is not 1.15 compatible)
The current version of Phat Loots is out of date.
https://www.spigotmc.org/resources/phatloots-loot-tables-conditions-block-loots-mob-drops-1-13-1-15.68925/
Double check that the server is whitelisted.
/whitelist on
If the server was whitelisted, one of the whitelisted users likely griefed the server themselves. Make sure everyone on /whitelist list is trusted.
Backdoor Flashback is a trojan horse (malware). Make sure you have antivirus software if you don't already. In the future, only download Minecraft from the official, trusted site, minecraft.net (this goes for any downloading-only trusted sites).
Minehut is an online network, so you cannot join with a cracked account. Make sure it's migrated and whatnot. Also try restarting your MC and see if that helps.
Resetting your password shouldn't delete your servers; make sure your old server wasn't deleted (check the dropdown menu at the top right).
If your problem is persisting, I recommend you contact support here. They are most likely to help you in account issues.