By default communication between storage account and cluster node happens on port 443 using TLS 1.0 which is vulnerable solution and block at most the servers. If TLS 1.0 is blocked then you will get error for cloud quorum setup in GUI. we can use below PowerShell commands to use TLS1.2 for cloud quorum setup.
[Net.ServicePointManager]::SecurityProtocol = [Net.SecurityProtocolType]::Tls12
Set-ClusterQuorum -CloudWitness -AccountName <StorageAccountName> -AccessKey <AccessKey>