I am running 2.14.3 and am unable to add a new website. I had this issue in the previous version as well, and I'm not sure how long this has been going on since I don't need to add websites often. I saw issues https://github.com/piwik/piwik/issues/7808 and https://github.com/piwik/piwik/issues/7802 but removing the showaddsite=1 parameter doesn't solve the issue, so it seems to be something different. I also tried re-uploading files and no luck. I have tried in Internet Explorer, Edge, and Firefox.
From the sounds it's related to #6497 maybe have a look here https://github.com/piwik/piwik/issues/6497#issuecomment-60836702 and at the other comments
@tsteur I just checked config.ini.php and it already included charset = "utf8".
@mattab Sorry for the delay... I updated to 2.15.0-b6 and the issue is not resolved.
Can you access your database and maybe have a look at the
piwik_site table? The table might be named
site or with a different prefix. There should be a column
name. Temporarily removing or replacing all umlauts or special characters may fix it. You should be able to edit them again afterwards via the UI and add the special characters again
@sndrsk could you give us access to your Piwik so we can see the problem? please email login credentials to hello at piwik.org if possible :)