could be TLS security related (ref: https://rnelson0.com/2018/05/17/powershell-in-a-post-tls1-1-world/)
Try this command first:
[Net.ServicePointManager]::SecurityProtocol = [Net.SecurityProtocolType]::Tls12
then try to do the update.
Note: the command only affects the current session and does not persist.
You may also check what version of TLS for client is set on computer. Looks like TLS 1.0 for client is required. (ref: https://powershell.org/forums/topic/wmf-5-1-upgrade-broken-repositories/)
Michael