I will show you how you can update a VCSA Appliance from command line rather then from webfrontend.
I assume you have configured a proxy server when you do not have a direct internet connection.
Login to the appliance at the console or by ssh.
First of all check the state of the lookup service by lsdoctor
Run the lsdoctor tool to recognized some certificate issues. Certificate issues are often the problem when an update fails.
Command> shell root@vCenter [ ~/lsdoctor-master ]# python lsdoctor.py -l 2021-12-13T12:52:04 INFO generateReport: Listing lookup service problems found in SSO domain... 2021-12-13T12:52:04 INFO generateReport: No issues detected in the lookup service entries