bulk imports not completing?

We have a 3rd party app in our instance to send Twillio SMS texts. We have looked at the logs, and from what we can tell, the app itself did request sending the text; however, when the app finishes processing, it has to tell Eloqua that it's done. That last step is just hanging, indicating to us that Eloqua isn't responding back that our request finished.

Any idea what might be causing the bulk imports to not complete?