I am trying to connect to an OPC HDA server (Proficy Historian) on a remote machine located on the local network. The client will be Ignition SCADA but I am using the free version of OPC Expert to Debug. Using OPC Expert on the server machine works fine and I am able to read data.
On the client machine, I get error 0x80040154 REGDB_E_CLASSNOTREG (Class not registered). I don't believe it is related to DCOM permissions. Previously, I had an access denied error but that went away when I made changes to the DCOM permissions.
OPC Expert suggests disabling and re-enabling OPC Features on the server machine. I have done this a few times without any luck. I have also re-installed OPC Core tools on both machines with no luck.
Sounds like you are using an OPC DA client to connect to an OPC HDA server. That will result in the REGDB_E_CLASSNOTREG error.