was there a solution to this problem? Because I’m having the same. Deleting config.ini.php and installing anew hasn’t helped, as Piwik ceases to function anyway as soon as I try to change the db settings in the new config.ini back to the old db (or more precisely: the new db I have set up with the dump of the old db). I then get the same error message again (already installed). As soon as I set back the db settings in the config.ini back to a fresh db everything works fine.
When I try to set the old db during the installation process I get the exact same message as gunwald - no chance to reuse the old tables. When I use a fresh db that has only been used for another failed piwik installation attempt before I get the option to reuse the old tables.
So, is it far fetched to assume there’s something wrong with the database I imported (tried it multiple times though)? How can I go about this?
Edit: Fwiw, I used MySQLDumper to back up my Piwik database after I had put Piwik in maintenance mode and stopped tracking. The size of the (uncompressed) backup file is 1.6 GB. I copied this file to the new webspace, restored the database content into a newly setup database - with the result described above.
2nd edit: I just saw that there are 133 tables in the original database as well as in the backup - but only 122 of them are restored to the new database, for whatever reason. Working on it now.