"No data has been recorded yet" after adding new Site

I have 2 sites running smoothly with piwik since years. Now i added a new site and i get this message since days…
"No data has been recorded yet"
I tried to change the address of the site, of the piwik place, but no change…
Looks like there must be some communication leak. But where??
When I go into Settings i get this error:
Fatal error: Cannot redeclare class Piwik\Plugins\UserCountry\LocationProvider\DefaultProvider in /home/www/0subdomains/piwik/plugins/UserCountry/LocationProvider/Default.php on line 115
Could this be the reason?

Thanks for any help.
Snote

Hi,

I am not sure if this causes your problem, but I know how to solve it:

The file [...]/piwik/plugins/UserCountry/LocationProvider/Default.php should have been deleted at some update some time ago and is now causing problems. You can simply delete it.

OK.
Thanks for this information. After deleting this default file, I got an error message with about 500 files to delete…
It is said i could delete all files using this command:

rm “/home/www/0subdomains/piwik/config/global.ini.auto-backup-before-update.php” …

Can somebody please explain me how to achieve this? I’m on a windows system.

Snote

Hi,

I think some future version of Piwik will also show the Windows commands there.
But you could just replace the piwik directory with the latest version similar to here:
https://piwik.org/docs/update/#the-manual-three-step-update

Thanks!
I already updated piwik. Now the problem seems to be that it only overrode the files and added the new ones, but didn’t delete the old ones. Therefore I have to delete all files and replace the whole installation.

But I think, that this is not the solution for my problem as the old registered sites are working without problem… It is only the new one which makes this problems.

Snote