BQ25895: NACK when reading a register through I2C communication

Hi, 

Please let me know if this question is appropriate in this forum. 

I'm having trouble reading a register in a slave through I2C communication. 

Slave: bq25895 http://www.ti.com/lit/ds/symlink/bq25895.pdf

IDE: Eclipse Neon

In main:

while (1){

   HAL_StatusTypeDef status = HAL_OK;

   uint16_t return_value = 0;

   status = HAL_I2C_Mem_Read(&hi2c1, 0xD4, (uint16_t)(0x07), I2C_MEMADD_SIZE_8BIT, &return_value, 1, 1000);

   if(status != HAL_OK) { printf ("Error");}

   else {printf ("No error");}

}

Problem: The I2C_FLAG_AF is set since there is no ACK from the slave. 

Tracing the problem down: 

/* Send Slave Address and Memory Address */

if (I2C_RequestMemoryRead(hi2c, DevAddress, MemAddress, MemAddSize, Timeout, tickstart) != HAL_OK)

/* Wait until TXIS flag is set */

if (I2C_WaitOnTXISFlagUntilTimeout(hi2c, Timeout, Tickstart) != HAL_OK)

/* Check if a NACK is detected */
if (I2C_IsAcknowledgeFailed(hi2c, Timeout, Tickstart) != HAL_OK)

/* Check if NACK is set inside of I2C_IsAcknowledgeFailed() */

if (__HAL_I2C_GET_FLAG(hi2c, I2C_FLAG_AF) == SET)

How do I fix this problem? 

I'm new to this whole thing, so I appreciate any helps. 

Thanks.