A couple months ago (actually maybe in the spring?) Yahoo had a big hack happen to it. They sent out tons of security warnings and kept bugging people until they changed passwords. I don't know if this relates to what happened to you.
Do you have any other emails you can use? If so, try emailing them from your other email address and see if you can contact them that way. They should be able to get you back to normal.
I did eventually give Yahoo different email addresses as backups.
And yes, I LOVE that thing of "password does not work so we'll send you a new one to the account you can't access".... Which internet geek thought that up? It has to be an inside joke among network people.
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2021 F150 2.7
2004 21' Forest River Surveyor