Can't connect Sigfox backend to TW

Hello,

I followed the Sigfox extension to connect Sigfox to TW through batch_url.

I tried several things, but TW always reply 403 to the callbacks containing a 'null' batch:

http://MYIP/Thingworx/Things/SigfoxInterface/Services/CallbackDataBatch?appKey=MYKEY&x-thingworx-session=true&Accept=application/json&batch=null

My paramters are as follows:

URL Pattern: http://MYIP/Thingworx/Things/SigfoxInterface/Services/CallbackDataBatch?appKey=MYKEY&x-thingworx-session=true&Accept=application/json&batch={batch}

Line Pattern: {device},{time},{snr},{station},{data},{lat},{lng},{rssi},

Also tried with a pattern using ';' as delimiter, and other sets of data, not working either.

Thanks for helping.