InetLab

If there is a timeout sending the EnquireLink, the evEnquireLink event is not fired. Instead, you just stop the EnquireLink timer and we have no idea what has happened.
Can you please fire the evEnquireLink if the EnquireLink times-out?

EnquireLink waits response exactly a number of msec defined in Timeout property of the SmppClient class.
evEnquireLink fires when SMSC sends EnquireLink request.

If you use internal enquire link then in case when EnquireLink timeout
smpp client disconnects. You need to attach a evDisconnect event and reconnect the client.

Please refer to SendEnquireLink(object stateInfo) in SmppClient.cs ....

if (res.Status != CommandStatus.ESME_ROK)
{
StopEvent.Set();
StopEnquireLinkTimer();
return;
}

You just kill the timer and nothing else happnes (e.g. I am not seeing evDisconnect event get fired).

Perhaps you can fire some event to let us know that the call to EnquireLink failed?

Here I also stop the client and it disconnects. I think that we have network problem when we don't get EnquireLink response. In this situation I'm just trying to reconnect the client.

Is it sufficient for you to get evDisconnect event fired?

Yes, it would be fine for evDisconnect event to be fired.
Please let us know when that might be available.

Has this been fixed yet?
If not, please let me know when it might be available.

When you get EnquireLink timeout it raises evDisconnect event.
Please download last version and check this.