I am trying to enable soft deletion of containers during creation of the storage account but the checkbox is greyed out and the Sign up for container soft delete link takes me to documentation page.

The output of below command shows the ContainerSoftDelete RegistrationState is stuck at Registering.
Get-AzProviderFeature -ProviderNamespace Microsoft.Storage -FeatureName ContainerSoftDelete
FeatureName ProviderName RegistrationState
ContainerSoftDelete Microsoft.Storage Registering