One day, appeared to be out of nowhere two of my existing web maps stopped working and refused to be opened. That is from the Windows version of Collector (now depreceated). All of the other web maps were working fine, but we these two when I tried opening they just said " ______ could not be opened" . After rebuilding maps, recreating feature services, re-adding items in AGO, nothing seemed to work. Then I realized that I recently added a Zip code polygon layer to both of these maps. I rebuilt the web maps entirely now, and they were working, the moment I went to symbolize the zip code polygons with a patterend/dotted line chosen in the AGO web map symbology, that is when the maps stopped working.
I've always wondered how ESRI still struggles with certain symbologies when it comes to web mapping, like why can't you do hatching or cross hatching in a web map? This appeared to be the same issue, only the problem never identified itself, instead it caused the web map to just refuse to open. Another issue with Windows version of Collector is that it can't use all of the new vector tiled basemaps, and thus you must find the REST URL of the old "World Street Map" .
All in all I can't wait until the ESRI completes the design for "Field Maps for windows 11", because we have people here who do all post field editing in collector because of it's simplicity it is the way to go. Also, hopefully my local government IT dept goes to Windows 11 soon 🙂