Call back is not calling

I am trying to opening UART bearer but call back function cbEvhBearer is not calling and it is returning -44.

in .c file:

/* Open the UART bearer */
bearerRet = wip_bearerOpen ( &br, PPP_BEARER, cbEvhBearer, NULL );

in .h file:
s8 wip_bearerOpen( wip_bearer_t *br, const ascii *device, wip_bearerHandler_f brHdlr, void *context);

typedef void (*wip_bearerHandler_f)( wip_bearer_t br, s8 event, void *context);

Please guide me.

As per my understanding -44 corresponds to PPP echo.