Powershell Remoting into None-Domain server issue

Can anyone help with the following problem?
I am trying to remote into a server (SVR_A) that is not part of the domain from the server(SRV_B) in a company domain. I can ping each server (SVR_A to SVR_V and vise versa). WinRM is running on both servers and Enable-PSRemoting is configured correctly in both cases. The SRV_B also has added the SRV_A to its TrustedHosts list.

get-item WSMan:localhostClientTrustedHosts


 WSManConfig: Microsoft.WSMan.ManagementWSMan::localhostClient

pe            Name                           SourceOfValue   Value
--            ----                           -------------   -----
stem.String   TrustedHosts                                   SVR_A

The SRV_A is one of the web servers in our DMZ, so there are other web servers that are not part of domain. I can remote into web servers using Invoke-Command or Enter-PSSession, but not from the App Server (SRV_B) which is in company domain.

I get this error:

(SRV_A) Connecting to remote server SRV_A failed with the following error message : The client
cannot connect to the destination specified in the request. Verify that the service on the destination is running and
is accepting requests. Consult the logs and documentation for the WS-Management service running on the destination,
most commonly IIS or WinRM. If the destination is the WinRM service, run the following command on the destination to
analyze and configure the WinRM service: "winrm quickconfig". For more information, see the
about_Remote_Troubleshooting Help topic.
    + CategoryInfo          : OpenError: (SRV_A:String) (), PSRemotingTransportException
    + FullyQualifiedErrorId : CannotConnect,PSSessionStateBroken

Powershell Version on both end

Name                           Value
----                           -----
PSVersion                      4.0
WSManStackVersion              3.0
CLRVersion                     4.0.30319.42000
BuildVersion                   6.3.9600.19170
PSCompatibleVersions           {1.0, 2.0, 3.0, 4.0}
PSRemotingProtocolVersion      2.2