Looking for logging into the Piwik Problem site and are not getting the correct working link for it? In such a case, you can use the links given here by searching your desired login page in the search box. If the page is present on our website then you will get all the links related to the Piwik Problem site. After that you can login as usual with your login credentials.
https://www.nobbis.net/nobbis-blog/18-piwik-und-mein-problem-mit-dem-login.html
https://forum.matomo.org/t/probleme-beim-login/15072
https://github.com/matomo-org/matomo/issues/9339
https://github.com/matomo-org/matomo/issues/12498
https://github.com/matomo-org/matomo-mobile-2/issues/2244
https://www.umwelt-plakette.de/piwik/
http://community.cloudways.com/t/piwik-wordpress-cannot-login-to-piwik-form-security-failed/380
http://www.staedelverein.de/piwik/index.php
http://caricatura-museum.de/piwik_cmf/
https://de.wordpress.org/plugins/wp-piwik/
https://www.blaue-plakette.de/piwik/
https://absv.de/analytics/
https://www.bw-lv.de/piwik/