Hi.
Well to be honest, I'm not 100% sure how this service was setup. Where I work the GIS users have no access to publish their own services, so we just submit a ticket to our IT help desk with an attached .mxd or .aprx file and they create the service. We just get the URL sent back to us with no control over how things are created.
From the responses above, and some blog/community articles, it seems like there are two issues here.
1. however this webservice was created, it won't work in AGOL. So I guess our backend needs to be updated? From what IT is telling me, our REST services are at v10.91....does that make sense??
2. We also have an onsite Portal, where the option to add related features to a pop-up aren't supported either, but I read somewhere that functionality is coming in Q4 of this year....is that correct?? But I guess if our REST is still at an unsupported version, then it doesn't really matter if Portal will support it or not.
A lot of moving parts here!! 🙂
I will try the @KenBuja method using Arcade to see if I can at least get something in there for now.