I get this message about once a month for all of my Yahoo accounts on my Windows phone.
Generally, going to the settings and re-entering the password fixes it.
However, today I had to uninstall the affected account and re-add it. Perhaps whatever bug messed up my sync did yours, too. Did you try removing it & re-adding it?
On the flip side, if you just added 2-step verification, that may also be why it doesn't sync (because you need to get that key everytime). <Just a guess and/or sync is incompatible with 2-step. I don't use 2-step, can't say for certain.
Also! I discovered this week, that if you switch 'on' the "Block insecure apps from connecting," you crippled your Windows mail app. I got an email from Yahoo, once I switched this on, bragging that they blocked an unauthorized attempt.. which I later found out, was me! The email they sent tells me to check my mail via Android & Iphone apps (notice how Windows apps are missing?)
No way to reach out to Yahoo and ask why they leave a legitimate phone OS off the 'secure apps' list. Not sure if this happens on the desktop version of the Yahoo mail app for Windows 10, also.
07-23-2016 12:14 AM