The file exists in the path where the error log says it does not exist. The WP installation is in a sub folder in the public html folder. The login file is in the root of that folder. I looked at another WP installation I have on the same site that is working fine and the problem WP site is configured the same way as the one that works.
I have an html site with 2 WP installations within the site. I know that’s not really recommended but it has worked fine for years that way. As far as I know, all that has changed since the site was working fine is the the updating of WP, themes and plugins. Unfortunately, those updates were all done at the same time so I don’s know which caused the problem. I have a backup that was done shortly before the problem but it’s difficult to run the restore without access to the dashboard.