First things first, you can update expired credentials from one of two places, your Profile tab or your Credentials tab. Updating a credential on one will automatically upload it to the other, so it is just your preference on where you want to access it from.
How do I update an expired credential from my Credential tab?
Hover over the expired credential you'd like to update, then click the Edit (pen) button.
A form will slide out from the right.
Be sure to update all fields you see below when updating your certification.
Be sure to update the expiration date to make sure your certification is active.
Be sure to delete (trash can) the existing file attachment, then upload your updated certification.
When you are done editing, don't forget to Save!
To cancel any changes you've made, simply click the left arrow in the top bar. You will be prompted "You have unsaved changes. Are you sure you want to leave without saving?" Just click 'OK' and your changes will not save.