Add existing Win SOFS SMB server to VMM

I have an existing SOFS in my environment composed of two VMware VMs.  I'm trying to add the SMB fileserver to VMM.  Using the wizard I specify the host name (I've tried using the file server cluster name, the cluster hostname, and a node name) and a runas account (my runas account is a domain admin and is explicitly added as a local administrator on the file server nodes).  The VMM computer account and the runas account also have full permissions on the individual shares.  The error I get back from the wizard is:

Registration of the storage subsystem perf-smb3.perf.local for user perf\testlab failed from perf-vmm.perf.local with the error code StorageSubsystemNotFound.

Specify a valid subsystem name, and user credentials for registering the subsystem.

ID: 26311

I've been futzing with the powershell commandlet in hopes of getting a more actionable error message, but I think I'm just missing something there.  I'm trying:

Add-SCStorageProvider -Name perfsmb -RunAsAccount $runas -NetworkDeviceName \\perf-smb -TCPPort 445

I've tried multiple device names on the command line and with and without the double whack.  The error I get back each time is:

file://perf-smb.perf.local:445 for user perf\testlab failed from perf-vmm.perf.local with error code HostAgentFail. (Error ID: 26263)

I also tried specifying exact shares...

I can add individual HyperV computer accounts to the shares and then register that storage path in the properties of the HyperV host in VMM and then create and deploy VMs on it, so it seems that the file share is working appropriately.

Any ideas?