51822 esb datarate 250kpbs cann't work!!

(void)nrf_esb_init(NRF_ESB_MODE_PRX);
		//nrf_esb_set_output_power(NRF_ESB_OUTPUT_POWER_0_DBM);
		nrf_esb_set_channel(18);//2400+18
nrf_esb_set_crc_length(NRF_ESB_CRC_LENGTH_2_BYTE);
nrf_esb_set_base_address_length(NRF_ESB_BASE_ADDRESS_LENGTH_4B);
		nrf_esb_set_address_prefix_byte(0,0x55);
		nrf_esb_set_base_address_0(0x3412BBAA);
		nrf_esb_set_datarate(NRF_ESB_DATARATE_250_KBPS);
(void)nrf_esb_enable();

when i set datarate NRF_ESB_DATARATE_1_MBPS or NRF_ESB_DATARATE_2_MBPS it was work,but when i set datarate NRF_ESB_DATARATE_250_KBPS it wasn't work,(Receiving and sending the same)