Can't change my description in header.php

I added a meta tag description to my header.php, however, now I am trying to change the description, but it will not let me change/update it. I try to make the change on header.php under appearances/editor. Then I hit the button at the bottom that says “update file”, but it reverts back to the header.php before I made the change, and my updated information is not there.

Any Ideas?

Thank you in advance