If you mean when you connect to the web admin portal through your browser, you have to renew certificates engine side.

If you have a self hosted engine you have to put the environment in global maintenance first. 

Then, both on standalone engine and on self hosted engine environments, you have to run this as root on the engine server:

engine-setup --offline

The --offline is because you don't update any package in case there are any available.

At the questions you should also see:

Renew certificates? (Yes, No) [Yes]:

and answer Yes

The other ones you can accept default answer

If you have a self hosted engine you have now to exit from global maintenance

See also here:

HIH,

Gianluca