too few aircraft, at least 2 required?

Hello, On the flightradar24 feeder it always says - too few aircraft, at least 2 required?

I am using an RTL2832U / R820T with a 16 element 1090mhz collinear antenna

I start the RTL1090 Beta2 software, within a minute its showing 6 to 8 aircraft, within 10 minutes its showing 28 aircraft
but the feeder always says - too few aircraft, at least 2 required

RTL1090 is set to Mode S, I also tried Mode AC but it doesn't work either.

GND: YES
Mode-S: NO
Protocol:TCP
Basestation: OK
Info: - too few aircraft, at least 2 required
Network:OFF
TX/AC Loss 0.0%/0.0%

what am I doing wrong?
also I noticed the text on RTL1090 is off the screen? how can I increase the size of the window?

thanks