Interrupt not entering the if statement

Hello!

I'm trying to figure out why my ISR is not entering the if statement.

            if(p_ctrl->smb_status_FLAG == SMB_STATE_IDLE)
            {
                p_ctrl->smb_status_FLAG = SMB_STATE_START;        //Next state is START
            }

The p_ctrl is a pointer to the structure:

typedef struct st_smb_instance_ctrl
{

    volatile smb_state_t smb_status_FLAG;

    /* Current transfer information. */
    uint8_t     *   p_buff;         /**< Holds the data associated with the transfer */
    uint8_t            rec_buff[SMB_REG_TAB_LEN];    /**< Holds the data associated with the receive transfer */
    uint32_t        total;          /**< Holds the total number of data bytes to transfer */
    uint32_t        remain;         /**< Tracks the remaining data bytes to transfer */
    uint32_t        loaded;         /**< Tracks the number of data bytes written to the register */
    uint32_t        received;       /**< Tracks the number of data bytes received during transfer */

} smb_instance_ctrl_t;

And the smb_state_t is a type of enum:

typedef enum e_smb_state
{
    SMB_STATE_IDLE =0,
    SMB_STATE_START,
    SMB_STATE_RECEIVE,
    SMB_STATE_TRANSMIT,
    SMB_STATE_COMMAND,
    SMB_STATE_TXSTOP,
} smb_state_t;

I'm pretty sure that the if statement should give a "true" (smb_status_FLAG was initialized as SMB_STATE_IDLE) and step into it, but during the debbug process I can see that this is not the case...

Could anyone help me to understand why this could happen?

Thank you for any hint!

Regards,

Gregor