The iTunes on my Mac is automatically updated to the latest version 12.7.4, and this version does not have the AppStore, which is frustrating. . Silently uninstalled this version and installed the latest 12.6 version.
Unexpectedly, after installing it, logging in to the iTunes account keeps prompting: Unable to complete your itunes store request, an unknown error occurred (-50)
Searched, most of the problems on the Internet were around 2011 and 2012, and the solutions provided were useless to me. After groping for a while, I found a solution: Open iTunes Preferences - Advanced - Click on Reset Warnings and Reset Caches below