I was having an issue where an entire device (a new M1 iPad Pro)was not showing up at all on any of my other devices. I tried switching safari syncing off in the iCloud preferences, logging in and out, changing the date and time, force rebooting… nothing worked.
What ended up working for me was closing all the safari tabs on the iPad. Waiting a minute, then force quitting safari. For good measure, I then rebooted the iPad. Once it restarted, I opened a few tabs. The iPad finally started showing up on other devices and seems to be working fine now.
In order to not “lose” my tabs, I simply bookmarked them or saved them to Notes so I could re-open them afterwards if I wanted to.
I know the above may not work for everyone, and may not work for those who have phantom tabs showing up or other syncing issues. But I wanted to at least share what my problem was, what I tried, and what ended up working — just in case it’s helpful to anyone else.