Yesterday also very big open between JA to Europe. I can QSO yesterday too.
However, the band was big open therefore many station QRV on the band. So sometimes QRM happened.
That mean, I found -10dB signal and called. Normally very easy return to my call then start QSO.
But if many QRM has, I called and maybe. There show my signal but no decode. Therefore there no return. I think there negative copy my signal then I change call for another station.
After that, before call station can decode and return to my call. However I call another station and start new QSO.
Actually 2 stations call to me show in the screen. But I can QSO for only 1 station.
This problem happen of a few time in yesterday. Condition was so good.