Sending of username did not succeed: Mail server pop.zoho.com responded: User already specified

Sending of username did not succeed: Mail server pop.zoho.com responded: User already specified

I am having issues receiving emails from Zoho in Thunderbird.  I am getting the above error.  The first error tells me Authentication failed, and prompts me to enter in my password.  Then I get the above error.  I can receive emails when I log in online to zoho, but for some reason, it's stopped working in Thunderbird.