Possible bug

I recently downloaded the tool and attempted to follow the install and set up instructions but I am still not able to get the FSrealWX tool to connect to FSX. I am on Win 10 and using the Stream FSX. When I go to the Interfaces menu it has SimConnect and FSUIPC& SimConnect greyed out. The CONNECT button shows an error
04:01:55:029 - (ConnectWorker) - Next Job ID: 1, Name: Connect
04:01:55:030 - (ConnectWorker) - not connected, Sim not Found
04:01:55:030 - (ConnectWorker) - Job finished ID: 1, Name: Connect
04:01:55:034 - (Controller) - JobID:1 JobName:Connect Finished, Error: 1

Occasionally I've seen an ERROR: 200 as well.

Your flight must be loaded into FSX, the plane must be parked, and then you can click the "connect" button in the FSrealWX program. Do you do that?

I still get the same behavior. Does the flight plan need to be built in FXRWX first before starting FSX? The instructions are not clear.

No, you don't have to create a flight plan, I don't use it at all.
Show screenshots of settings in the "Weather" and "Interface" tabs. If you click the "Test Connection" button on the "Interface" tab, what are the messages in the test window?