Sometimes, sending from one exchange to another might encounter some delays. I am sure if you check through blockchain explorer, you would see that it has been sent from coinbase, but you can still confirm that. The delay might be as a result of network.
I think next time, you can try to send first to your offline wallet, if you do not mind the transaction fee you will use in sending back to exchange.
To put your mind at rest, you will still receive it, just that it might take some time.