Password doesn't work

I can't reset my password. For some reason, the password - which is stored on my apple devices automatically - isn't working, and I'm not receiving the reset emails (it's a Yahoo account). I've tried adding no-reply@dropbox.com to the contacts and tried again, but nothing. I can access the browser account via my dropbox app on my laptop, but I can't access the account via my phone. And I can't change the password once I'm in the account on my browser because it wants my password... I have backup codes for the account - but I can't see where to enter them if I don't have access to the password, and my phone number is on the account but I'm not getting a message via the phone. I have asked for help via the contact us page, and Dropbox have emailed to say that they will get back to me in 1-2 days - I got that email ok, I'm just not getting the no-reply emails. And it's impossible to contact Yahoo unless you have a premium account - the chat bot was not helpful. 

Does anyone have a suggestion??