I can’t find my wordpress admin page

Try manually resetting your plugins (no Dashboard access required). If that resolves the issue, reactivate each one individually until you find the cause.

If that does not resolve the issue, access your server via SFTP or FTP, or a file manager in your hosting account’s control panel, navigate to /wp-content/themes/ and rename the directory of your currently active theme. This will force the default theme to activate and hopefully rule-out a theme-specific issue (theme functions can interfere like plugins).

I suspect that you changed the site and home url inside your settings >> general from HTTP to HTTPS, hence resulting in this error.

You can login to your Cpanel then phpmyadmin to manually rewrite the URL back to the HTTP version and you should be able to login normally.

Reference link – https://help.dreamhost.com/hc/en-us/articles/214580498-How-do-I-change-the-WordPress-Site-URL-

Hope this helps!

Thank you @t-p and @websprout, I really appreciate your help.