WeMo binding not working

I’ve just updated to OH2.1 and started using the WeMo binding with a WeMo Switch. Until now I was managing it with a shell script (http://moderntoil.com/?p=839 this one, a little modified) and it worked perfectly. I can’t remember why I wasn’t using the WeMo binding in OH1.
It doesn’t work most of the time. I’m getting this message every 2 minutes:
2017-12-13 10:47:56.658 [ERROR] [ome.binding.wemo.handler.WemoHandler] - Failed to get actual state for device ‘wemo:socket:WeMoSalon’: Could not call WeMo
And almost every time I issue a command I get this:
2017-12-13 10:20:49.299 [ERROR] [ome.binding.wemo.handler.WemoHandler] - Failed to send command ‘OFF’ for device ‘wemo:socket:WeMoSalon’: Could not call WeMo
The thing is online in Karaf (and it was autodiscovered correctly by OH2, that’s how I found the UUID):
openhab> smarthome:things list | grep wemo
wemo:socket:WeMoSalon (Type=Thing, Status=ONLINE, Label=WeMo Switch, Bridge=null)
And the script still works:
./wemo_control.sh GETSTATE
I think I haven’t updated the switch since I bought it a few years ago. Is there a minimum version for it to work? Is there anything else I can do to find the error?