Login page fails: refreshes without error on form submit, recovery page refreshes with ERROR: Enter a username or email address

I run WordPress on IIS10 on Windows Server 2016. When I try to login the page simply refreshes without any logged errors (not on screen, developer console or WordPress logs).

When I try the WordPress lost password screen (wp-login.php?action=lostpassword) and enter my username or email address I get:

ERROR: Enter a username or email address.

I tried everything as suggested here:

• https://www.wpbeginner.com/wp-tutorials/how-to-fix-wordpress-login-page-refreshing-and-redirecting-issue
• I can’t access my site via wp-admin
• Can not login with correct username and password
• Show errors on custom login form
• I can’t access my WordPress dashboard – shows Warning message

To summarize what I tried:

• Renamed folder ‘plugins’ to ‘plugins_backup’
• Ran UPDATE wp_options SET option_value = 'a:0:{}' WHERE option_name = 'active_plugins';
• added lines to wp-config for
  define(‘WP_HOME’,’https://www.example.com’);
  define(‘WP_SITEURL’,’https://www.example.com’);
• template is reset to “twentyseventeen”
• deleted cookies
• set WP_DEBUG and ‘WP_DEBUG_LOG’ to true in wp-config, though still no errors show when trying to login and also no logfile is created in wp-content folder.
• [wp_usermeta] wp_capabilities field for my user has value a:1:{s:13:"administrator";b:1;}, so I’m an admin
• Repaired all MySQL database tables via mysqlcheck -r [database]