Ironically, in the installation process Piwik complains that “Some tables in your database have the same names as the tables Piwik is trying to create”.
Go figure. Only options are to “Go back and define a Prefix for the Piwik Tables” or to “Delete the detected tables”. Obviously I want neither. Any help?
If you copy the file “/config/config.ini.php” from the old server to the new, after making whatever changes are necessary to tell Piwik that it’s running on a different server, Piwik won’t try to do a “new” install. It should just pick up the relocated database, and start to work normally.
In other words, manually edit the configuration file (it’s just a text file) and then launch Piwik in its new location. (Assuming, of course, that you previously moved the database and all its tables.)