I had the same problem with constantly searching for a link to log in to the Shopify admin panel. The most convenient solution is to save it to your browser bookmarks or pin it to the quick access panel. You can also use password managers, they immediately save the link and login data. If errors occur, you should check whether the address is entered correctly or refresh the browser cache. It is important to know that access to shopify admin panel must be protected: use two-factor authentication to avoid problems.