Hand-off stopped working

Until recently, I've been typing text on the laptop (MBP 2019, 15.1.1) to paste into SMS on the iPhone.  That quit working yesterday.  Photo sync and Notes sync still works, so now I type in Notes and copy on the phone to paste in Messages. Hand-off is ON in both devices. After it refused to work twice in the past fifteen minutes, I started this post.  But now it's working again. **What, with no settings changes, could make Hand-Off not work for about 24 hours without affecting other iCloud functions?**