Why won't my zoho mail SEND?

Why won't my zoho mail SEND?

I don't understand.  Once a month, like clockwork, I'll be logged in to Zoho.  I just completed writing an email and then I click SEND and nothing happens.  It's not my internet connection because I have gmail up on a different tab in my browser and it ALWAYS works.  So, I click send and nothing happens.
I try closing the email and then I save it as a draft.  Then, I log out and reboot my computer.  I open Zoho Mail back up, go to Drafts and try to send my email again and nothing happens.

UGH!!!  $%#&*()$$^*(@#!!!

There's a little box that appears that says:  SENDING _______________  but nothing happens!!
SO FRUSTRATTING!!!!!!!  Why are my emails NOT BEING SENT today????????????