How to restore Admin access for failed TLS/SSL access with phpMyAdmin
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Symptoms: TLS/SSL Socket 443 failure is preventing access to my Administrative (backend | control panel) or my Admin has been set to use secure access before TLS/SSL has been activated
1. Open your core_config_data table in phpMyAdmin.
2. Find the row with the path web/secure/use_in_adminhtml and change its value field from 1 to 0 to enable accessing admin panel from unsecure http://www.yourwebsite.com url
Changing web/secure/use_in_frontend toggles customer shopping cart security, 1=on and 0=off which probably isn't of importance as you're trying to regain administrative access
3. Clear /var/cache, /var/session and reindex your URL_rewrite index after changing base_urls. This is necessary because your config is cached and clearing it forces a reread of the configuration data from the core_config_data table.
You should now be able to access your Magento Admin panel by standard unsecured web access (port 80, http).
NOTE: Be aware that accidentally entering your leading https:// instead of http:// on your unsecure_base_url before you have enabled TLS/SSL on your webserver will lock you out, so if the above doesn't get you in, look for rows with web/unsecure/base_url and check for the aforementioned misconfiguration