use the api "otCommissionerAddJoiner" can't into OT_COMMISSIONER_JOINER_CONNECTED

void CommissionerJoinerCb(otCommissionerJoinerEvent aEvent, const otJoinerInfo *aJoinerInfo, const otExtAddress *aJoinerId, void *aContext)
{
    uint8_t i;
    printf("CommissionerJoinerCb.evt = %d\r\n", aEvent);    
    switch(aEvent)
    {
        case OT_COMMISSIONER_JOINER_START:
            printf("OT_COMMISSIONER_JOINER_START\r\n");
            if(aJoinerInfo)
            {
                printf("mType = %d\r\n", aJoinerInfo->mType);
                printf("mEui64 = \r\n");
                for(i = 0; i < sizeof(aJoinerInfo->mSharedId.mEui64.m8); i++)
                    printf("%02x ", aJoinerInfo->mSharedId.mEui64.m8[i]);
                printf("\r\n");
                printf("mPSKd = %s\r\n", aJoinerInfo->mPskd.m8);
                printf("mExpirationTime = %d\r\n", aJoinerInfo->mExpirationTime);
            }
            break;
        case OT_COMMISSIONER_JOINER_CONNECTED:
            printf("OT_COMMISSIONER_JOINER_CONNECTED\r\n");
            break;
        case OT_COMMISSIONER_JOINER_FINALIZE:
            printf("OT_COMMISSIONER_JOINER_FINALIZE\r\n");
            break;
        case OT_COMMISSIONER_JOINER_END:
            printf("OT_COMMISSIONER_JOINER_END\r\n");
            break;
        case OT_COMMISSIONER_JOINER_REMOVED:
            printf("OT_COMMISSIONER_JOINER_REMOVED\r\n");
            otError error = otCommissionerAddJoiner(instance, &extAddr, PSKD, 120);
            if (error != OT_ERROR_NONE) {
            printf("Failed to add joiner: %d\r\n", error);
            }
            break;
    }
    if(aJoinerId)  
    {
        printf("aJoinerId = ");
        for(i = 0; i < sizeof(aJoinerId->m8); i++)
            printf("%02x ", aJoinerId->m8[i]);
        printf("\r\n");
    }
}
this is my api,i find my joiner to start join,the log is 
CommissionerJoinerCb.evt = 0
OT_COMMISSIONER_JOINER_START
mType = 1
mEui64 =
00 12 4b 00 14 f9 ce 49
mPSKd = DRRLCK8
mExpirationTime = 16579
aJoinerId = 9e 76 93 2b b1 9e 4f 63
CommissionerJoinerCb.evt = 4
OT_COMMISSIONER_JOINER_REMOVED
aJoinerId = 9e 76 93 2b b1 9e 4f 63
Why is this the case?
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