Installing / Upgrading Data Gateway but not getting option to Migrate

We have been advised to upgrade the Data Gateway (Enterprise) every month, after our 6m old gateway died on us last month, so this is our first month of doing so.

I've been following the instructions on https://powerbi.microsoft.com/en-us/documentation/powerbi-gateway-onprem/

However i'm not sure if it has completed successfully!

After running the Installer and being asked to Sign In, it does not proceed to give us the option to migrate / restore / takeover.  I'm using a different account to do this than i did last time, although both are admins on the existing gateway.

Provided the account you are using is an Administrator on the existing Gateway, does it just complete the upgrade automatically?  Or could it be that the version has not changed since we last did it? (I havent been able to find a version history of the data gateway online).  Do I need to restart the Gateway?  (It didnt due the usual microsoft warning of saying it was still running before it could go ahead).

Does anyone know how i can check if the Gateway has definately been upgraded successfully?  I can see the current version in Control Panel is 1.15.6170.1.

Thanks