vnams

Both page.php and single.php have that code in there. index.php doesn’t. I put it in now but it has no effect.

Note that I have this problem even using the Classic and the Default themes.

Might there be some kind of permissions problem?

Yes, it includes a comments.php file.

I found the problem. After trying many more suggestions in past posts, I copied a new version of wp-login.php, and now it works fine.