Authentication issue when redeploying the APP

Hi,

I've never done IOS development before but have to unfortunately inherit an in-house developed/deployed IOS app. App is developed in SWIFT with Alamofire 5.6.2 and connects to services hosted in Windows. The current deployed version works fine on phones/ipads but due to various issue with the previous app account holder we need to re-deploy it.

We managed to get the code compiled and run with XCode. When the app is packaged up with a new distribution certificate, it does not seem to connect to our services after deployment (the app is deployed fine and can be launched). While it runs on the MAC itself (MAC is joined to the network and domain), it does not run if I use any simulators -- we get 401 authentication failure.

Anything we are missing here? Given no experience in IOS before it is rather hard to even start searching.