I got trouble today and client certificate is not working, so I follow the instruction here :
https://help.salesforce.com/articleView?id=000240906&language=en_US&type=1
5. How do I create a self-managed client certificate for the API Client Certificate?
1. Create a Salesforce self-signed client certificate or your own CA-signed client certificate in the Certificate and Key Management setup page. 
NOTE: The CA can be an Active Directory Certificate Services signing certificate; it doesn't need to be a third-party trusted CA.
2. In the API Client Certificate section of the Certificate and Key Management setup page, click the Edit button to change the org's API client certificate.
3. In the API Client Certificate edit screen, choose the API client certificate to use and press Save.

I can create a self-managed client certificate, but I can't  do step 2 because I can't find " API Client Certificate section" on Certificate and Key Management setup page also I can't find " API Client Certificate edit screen," 

​Please help

Hello,
 
We are using lightning tab in my application. We have total 3 tabs and when i land on tab 1, i can go easily to tab 2 and 3 but when if I click on tab 1 again from Tab 1, I want to refresh / reload this tab but it does nothing.. How can i do that ? Any suggesions. 

Regards,