client certificate need it to log in to a web site

Does the web site load? What happens when you try to log in? Error message(s)?

Try setting up another admin user account to see if the same problem continues. Also try the Safe Mode.

Safe Mode - About El Capitan
also Sierra

Safe Mode Startup – El Capitan. also Sierra

If it works in the Safe Mode, try running this program when booted normally and then copy and paste the output in a reply. The program was created by Etresoft, a frequent contributor. Please use copy and paste as screen shots can be hard to read. Click “Share Report” button in the toolbar, select “Copy to Clipboard” and then paste into a reply. This will show what is running on your computer. No personal information is shown.

Etrecheck – System Information

Hi,

On the MacBook Pro running High Sierra ...

Launch Safari then go to the menu bar, click Safari > Preferences then select the Privacy tab then click: Manage Website Data.

Then type in the name of that website in the search field top top corner of that window then click Remove > Done.

Quit and relaunch Safari then try logging in to that website.