WordPress login issue

try:
– switching to the default theme by renaming your current theme’s folder in wp-content/themes using FTP or whatever file management application your host provides.

– resetting the plugins folder by using FTP or whatever file management application your host provides. Sometimes, an apparently inactive plugin can still cause problems.

– renaming or deleting the .htaccess file after making a backup of this file by using FTP or whatever file management application your host provides.

– check file permissions. All directories should be 755 or 750. All files should be 644 or 640. Exception: wp-config.php should be 600 to prevent other users on the server from reading it.

– re-uploading the wp-admin and wp-includes folders from a fresh download of WordPress by using FTP or whatever file management application your host provides.