Running sports commentary from ISDN mixer to Macbook

Hi, first-time poster and something of a novice (in case my enquiry as follows makes no sense!).
I was tasked with producing live streaming for a football club this past few months and while the video element of it has gone very well, linking audio commentary has been more of an issue.
For reasons out of my control, rather than just plug two headsets into an input next to our camera position, I need to share our local radio station's commentary from a position 50+ yards away.
So currently, I have a poor-quality setup where two nearby mics pick up their voices, run the signal through a long XLR lead, into a USB audio interface and then to the laptop. It works, but their voices mingle with background noise, wind and the fact they are not speaking directly into our mics but into their own headsets.
So what I'd like to do is run an XLR from the mixer output of their Glensound ISDN unit, taking their headset audio direct into the Macbook. I tried it with an XLR into our Behringer USB audio interface but the result was very muffled, full of static and background noise. They suggested I needed to run the XLR into a line-in in a mixer rather than into the mic input. Anybody know what if they're right and what I'd need to accomplish it.
I tried to visualise this a little better below...

I was tasked with producing live streaming for a football club this past few months and while the video element of it has gone very well, linking audio commentary has been more of an issue.
For reasons out of my control, rather than just plug two headsets into an input next to our camera position, I need to share our local radio station's commentary from a position 50+ yards away.
So currently, I have a poor-quality setup where two nearby mics pick up their voices, run the signal through a long XLR lead, into a USB audio interface and then to the laptop. It works, but their voices mingle with background noise, wind and the fact they are not speaking directly into our mics but into their own headsets.
So what I'd like to do is run an XLR from the mixer output of their Glensound ISDN unit, taking their headset audio direct into the Macbook. I tried it with an XLR into our Behringer USB audio interface but the result was very muffled, full of static and background noise. They suggested I needed to run the XLR into a line-in in a mixer rather than into the mic input. Anybody know what if they're right and what I'd need to accomplish it.
I tried to visualise this a little better below...
