Dell OMSA - SSL Version Greyed Out

The SSL Version is greyed out on our PowerEdge R310 - we need to set this as TLS V1.2 minimum

I've been able to adjust this setting on all of our R710's. 

I'm logged in as the master administrator account.

I've tried setting it using CLI tools but getting an error

PS C:\Users\Administrator\Downloads> omconfig preferences webserver attribute=sslprotocol TLSv1.2
Error! Invalid name=value pair: TLSv1.2

Any ideas please?

Thanks