caltrans CA California department of transportation
project map
https://odp.dot.ca.gov/sb1/
info window not popup after user click feature
Part 3, conclusion
The best way to avoid this issue, or best work around is to not use dynamic layers, not use map image service.
Use feature layer instead. From my previous test, feature layer works fine.
Keep in mind that this issue only happen with point and line layer, does not apply to polygon layers. Polygon layer is free of this issue because when you click inside polygon, this polygon always get pick up. However, you never can click inside of point or line, you can only click close to a point or line. when. you click too far away from a point or line, the issue occured.
caltrans layer most of them are point and line, not like city's layer most of them are polygon such as police beat, fire district, zoning, general land use, parcel. Caltrans layer are freeway, highway, they are lines.
Another idea is to use arcgis online instead of current portal. Because arcgis online does not provide map image service, which forced you to use feature layer.
Portal does allow you to use map image service like current apps. So the issue occured.
You could still use current portal but need to swap map image layer with feature layer to fix current issue.
Or you swap from portal to arcgis online, which forced you to swap map image layer to feature layer.