Looking for logging into the Joomla 1.5 No After Upgrade 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 Joomla 1.5 No After Upgrade site. After that you can login as usual with your login credentials.
https://forum.joomla.org/viewtopic.php?t=259959
https://www.itoctopus.com/login-to-joomla-administrator-not-working-and-no-error-is-displayed
https://joomla.stackexchange.com/questions/4957/unable-to-log-in-after-upgrading-joomla-2-5-to-3-0
http://www.pwrusr.com/web/cannot-login-to-joomla-backend-as-admin
https://stackoverflow.com/questions/15100615/i-moved-my-joomla-site-but-now-i-cant-login-to-admin-tools
https://www.siteground.com/kb/i_cant_log_into_the_joomla_backend_as_administrator/
https://community.spiceworks.com/topic/115465-joomla-login-issue-session-not-saving
https://github.com/joomla/joomla-cms/issues/8766
https://www.collectiveray.com/joomla/joomla-tutorials/joomla-blank-page.html
https://www.pobox.it/jcms/index.php/tips-tricks/11-no-login-to-joomla-2-5-x-after-upgrade
https://www.gavick.com/blog/joomla-when-youre-not-able-to-access-administration-panel
https://www.youtube.com/watch?v=VLt-WQCOCpw
https://www.krienke.org/de/techblog/33-joomla15to25