Generally speaking you are better off configuring pop ups in Pro.
With the feature your trying to configure. Is it JOINED to anything in your mxd or project?
Was it put into a relationship After you published what your trying to configure.
I would try republishing and then trying again.
it seems the issue is being caused by the feature service having a field in there twice, which is strange in it own right...
if we delete the field we get another error, i'll raise it with support and see what they say