This mainly occurs with outbound calls.(i.e when you are calling a user from your virtual number).
In this case, you initiate the call. You get the call 'Queued' response e.g :
Queued +254705123456 ATVId_897e123d38eda70fd6639db39ccdcd73
But you the call doesn't get completed and you can't see the log on your application dashboard.
Here are a few reasons this may happen.
The call was rejected by the recipient.
You do not have sufficient credit in your AT stash.
There's a connectivity issue is which case please reach us on firstname.lastname@example.org and we'll look into it.