Send To Kindle Problems

In trying to login to the “Send To Kindle” application on Windows I found that my valid username and password did not work.  I contacted support and, although helpful, they could not help resolve the problem.  I then remembered that I had 2FA enabled on my Amazon account.  I disabled 2FA and successfully signed into the screen below.  I then went back and re-enabled 2FA on my Amazon account.

After disabling 2FA I could sign into the app.