Very general way to fix wordpress redirect issues: (should work in all cases)
- /wp-admin/options-permalink.php Click "save changes". this will refresh WP redirect rules.
- check .htaccess, try to comment everything except WP part.
- Try to temporary disable plugins. Quick way is to rename wp-content/plugins/ folder, WP will not disable plugins, just will not load them. ATTENTION: do not visit /wp-admin/plugins.php when wp-content/plugins/ is renamed, becouse WP would auto disable them all.
- check your themes files, functions.php, try to activate WP another/default theme for test.
- If above do not work, download new fresh WP version.
TIP: try to never change files in wp-admin/ or wp-includes/ folder. These gives disaster in future.