'Connection Error Detected' on iPhone

I have Adobe Digital Editions on both my Macbook Pro and iPhone SE. Both had been working fine until recently, where I'm now getting an error message on the iPhone. The eBook I'm trying to load still loads perfectly on the Mac. However when I try and load it on the iPhone, it comes up with the following error message:

Connection Error Detected

Digital Editions could not connect to the fulfillment server. Please make sure you are connected to the internet.

I'm definitely connected to the internet so that isn't the issue here. I've tried deauthorizing my account, deleted the app and then reinstalling it and reauthorizing the account in the hopes a reset would fix the issue. Unfortunately it hasn't. What other steps am I able to take to fix this?

Given the error mentions a 'fulfillment server' I'm wondering if there's an issue on Adobe's side of the equation and not something I can fix myself.