no signals

[GM0ICF]

Hi,
I'm a newcomer to the Pluto and have just received one today. Got all the drivers and it seems to have installed ok. I can see the Pluto in the device manager.
Start up SDR console, add the radio, set the definitions, and hit start.
Everything came on as expected but I'm not seeing any signals at all. Nothing just an I/Q spike in the middle. The antenna is a small yagi and even with the I/Q not perfect on other SDR's there are plenty of FM radio stations to check with. (Can I manually adjust the I/Q?)
Re-started, re-installed, added an external USB power source, as I see that mentioned in other posts. I've tried various antenna.
Any suggestions as to what I'm missing or have not done correctly....?
Thanks,
Bill.