Please check the filters on the account to make sure there isn’t one set up that might make your emails go to the trash folder: https://help.yahoo.com/kb/SLN15994.html

In case you do not have any incoming mail filters set-up on your Yahoo account, please check the incoming mail filters, and junk mail filter, in the mail applications that you are using (e.g. Outlook, Mac Mail, Windows Mail, Thunderbird, mobile email application).