'Status code 400' error when connecting SQL data source to on-prem gateway

[alanperrott]

I have a connection to a remote SQL server data-source which works OK in PBI Desktop. I can add the data-source to the gateway in 'Manage Geteways' and the connection is successful. However, when I try to use the on-prem gateway for my datasource it fails with the unhelpful error "Something went wrong...", and a status code of 400. I have restarted the gateway service several times to no avail. I have turned on 'additional logging' but that doesn't show anything. Can anyone suggest why this might be failing, or advise how I can get more diagnostics?  

[alanperrott]

Thanks for the support Xiaoxin.

I have been through the gateway logs with 'additional logging' enabled and there are no errors reported.

I have installed Fiddler on the server - I presume that I have to use HTTPS Mode in the gateway for the data to be captured by Fiddler, so I have done this. Fiddler shows the various tunnels being set up, but other than that I don't see anything significant. When I try to apply the gateway connection to the dataset in PBI settings then I don't see any activity in Fiddler, but  then I'm not 100% certain what I should expect to see.

In PBI settings everything still looks OK until I try to apply the gateway to the dataset: the gateway is online and connection tests are successful; in the Dataset settings I can see that the gateway is available and online, but when I try to apply it then I get the 'status code 400' error. 

I am at a loss to know what else I can check...

Alan.