Import and Edit fails with Sierra SIM from mangOH

I’m having an issue with the SierraWireless SIM that came with mangOH Red.
When I use the “Import and Edit” feature on AirVantage, giving a .csv file with the ICCID for the SIM, it responds with failure and the message “A subscription already exists with this identifier”.

After this failed once, I retraced steps by going to

there is a button just for me: "If you are already the lucky owner of an AirVantage account, directly register your mangOH HERE. That takes me into my AV account, which seems promising, but when I try (under the “more general and lifecycle actions” pulldown) the Import and Edit gives the failure message above. I am certain that I have not used this SIM before. I have used this feature to import & edit other SIMs in the past, that were purchased directly from Sierra Wireless, so I think it has to do with the fact that it came from mangOH.

Could it be that I should enter something different in the SUBSCRIPTION[OPERATOR] column? I currently have SIERRA_WIRELESS in that column, which worked with the direct-purchased SIMs.

Any help greatly appreciated!

@thibs can you help?