Thanks for posting and I’m sorry to hear about your concern with your devices not appearing on your Nest Hub, specifically under “Linked to you”. Let’s find the solution for this. A few questions: the devices that don't appear on your Nest Hub, are they still available and connected to your Home app and is working as it should? What are those devices?
It would really be a big help if you could do a sequential reboot to refresh all connections between your devices. Unplug the power cord of your router followed by your Nest Hub and all other devices. Restarting your phone might also help.
Keep me posted.
@Discojudd, thanks for the help.
@clipperqb, I hope you've got the answer you're looking for. In addition to what they shared, you can do a factory data reset on the Nest Hub to out it back to its default setting and set it up as a new device. Check the step below on how to do it.
Here’s how to do the reset, press and hold the volume up and down button located at the back of your Google Nest Hub together for about 10 seconds. You'll hear your Google Assistant confirm that it's resetting your Google Nest Hub.
Check this link for more information.