Unable to transmit IQ samples with iio_writedev: "Unable to get sample size, returned 0"

[mr-aq-stack]

I'm trying to transmit a binary IQ file (sinwave.bin) using iio_writedev using ADRV9361-Z7035 setup with OpenWiFi. However, I'm consistently getting the error:
This is my tx_sinwave script:

#!/bin/sh
############################## Init ###############################
SAMP_FILE=sinwave.bin
LO_FREQ=2425000000
SAMP_RATE=61440000
TX_GAIN=10
RF_BW=56000000

iio_attr -o -c ad9361-phy voltage0 hardwaregain -${TX_GAIN}
iio_attr -o -c ad9361-phy altvoltage1 frequency ${LO_FREQ}
iio_attr -o -c ad9361-phy voltage0 sampling_frequency ${SAMP_RATE}
iio_attr -o -c ad9361-phy voltage0 rf_bandwidth ${RF_BW}

############################## Transmit ##############################
#while true
#do
echo "Transmitting data..."
cat ${SAMP_FILE} | iio_writedev -b 65536 -c cf-ad9361-dds-core-lpc &
echo "Data transmission complete."
#done

When I transmit it the attributed are written successfully but it gives error of sample size
root@analog:/home/analog# ./tx_sinwave
-10.000000 dB
2424999998
61440000
56000000
Transmitting data...
Data transmission complete.
root@analog:/home/analog# Unable to get sample size, returned 0

Error:
Unable to get sample size, returned 0