Mail account no longer shows

I have 7 e-mail accounts thru ATT/Yahoo.

There all work fine with one minor exception for one mail account.

The new mail (number of e-mails) does not show up in the left hand side Mailboxes in box (bullet)

There are listed when I click into the mail box (listings) with the round blue dot for new mail.

As I stated all the other 6 will snow the round bullet with the number of e-mails

Any suggestions on how to fix it.

Greg