I spent 30 minutes trying to reset the Presta Shop Admin password via PhpMyAdmin (MD5 (cookie+password)) with no luck.
To reset the password make sure you download and edit this file (it is part of the attachments in the above link) “prestashop_pword_hash.php”
Edit the file and change $cookieKey and $newPassword
Once done upload it to your webserver and run the file. Copy the output MD5 hash string from your browser and paste it into the “ps_employee” table under the “passwd” column and hit Go.
This should hopefully get you in.