I'm having the exact same problem. All my various WeMo switches and plugs are recognized in the WeMo app but I can't get setup to link my WeMo devices to my Google Home app. I keep getting the "A network issue occurred" for well over a year. My WeMo devices have been setup successfully to IFTTT & can be managed by IFTTT but that's limited compared to the capabilities of the Home app.
WeMo's shortcoming is frustrating especially since my LIFX lights, Nest thermostats and camera, Vizio TV, various Sony speakers, an LG Smart display, Brookstone speaker and multiple Chromecast Audio devices have all successfully been setup in the Google Home app which leads me to logically conclude the issue is with Wemo.