Check the _transfer settings in fop2.cfg
blind_transfer=x
supervised_transfer=x
Sometimes supervised transfer is not configured in features.conf so you cannot use it without enabling it, in that case you can try disabling it in fop2.cfg (supervised_transfer=0). So check your settings, and test with variations:
blind_transfer=1
supervised_transfer=0
or
blind_transfer=0
supervised_transfer=1
or even
blind_transfer=1
supervised_transfer=1
Best regards,
