I expect it is because, over the Christmas period, we have set the spacecraft to be in continuous amateur mode. this means that the transponder is operational 24/7 and the telemetry is only being transmitted with a downlink power of around 30mW rather than the usual 300mW.
I am pretty certain that this is why, with an omni antenna, you are not getting enough signal strength.
We plan to return FUNcube-1 to normal autonomous operation on Sunday evening. this will mean that, when the spacecraft is in sunlight, tit will be back in educational mode with the 300mW telemetry on.
Sorry if you have been inconvenienced!