Today when installing SQLServer module on one system I got the below error.
This happens because the TLS setting for PowerShell is not compatible with PSGallery.
Use the below script to set the session TLS version to 1.2 for the session
Net.ServicePointManager]::SecurityProtocol = [Net.SecurityProtocolType]::Tls12
Once doing this you will be able to install any module but you need to do it every time you are installing any new module.