how do I reinstall windows defender for windows 10

This is NOT the error I have, although it looks similar.

(You replied to your own post.) The error you're getting now is not the same error (i.e., 0x8050800d) you were getting on or about 17 May or...?

This is NOT the error I have, although it looks similar.

Assuming the upgrade was offered & installed via Windows Update => Does the behavior persist if you run the Norton Removal Tool (and reboot) and then the McAfee Consumer Products Removal Tool(followed by another reboot) anyway?

[You cannot "reinstall" Windows Defender.]

It does not install. Error code 577

My message was that Windows Defender was closed.  I was hoping that it would have been more information as to how to reinstall.  Did not mention error code 577

Please answer all four (4) questions by number:

1. Did the computer come with Win10 preinstalled or did you upgrade a Win7 computer or a Win8.1 computer [<=PICK ONE!] to Win10?
2. Has a Norton application or a McAfee application EVER been installed on the computer since you bought it?
3. Did a Norton free-trial or a McAfee free-trial [<=PICK ONE!] come preinstalled on the computer when you bought it? (Doesn't matter if you never used or Activated it.)
4. Have you ever run the Norton Removal Tool and/or the McAfee Consumer Products Removal Tool?

1.  Upgraded from Windows 7
2.   No
3.    No
4.    No  I am using AVG Optima