I'm having the same issue as a previous poster (dch) earlier this week, but the thread has been closed [https://www.googlenestcommunity.com/t5/Speakers-and-Displays/Nest-Hub-Max-Works-from-my-House-not-fr... . I wanted to ask if the "solution" that was reached was the travel router suggestion or if there was something else he/she did to overcome the "XXXXX Display may be setup, but we could not communicate with it from your iPhone. Make sure you have enabled local network access in your iPhone's Privacy Settings. Then try again," error. My father is completely reliant on the Google Hub voice commands for Duo since he doesn't have the manual dexterity to use a cell phone for FaceTime or other video chat application. Thank you!
So the answer for the post you referenced is "
the long and short is the Nest devices are designed to work on a secure personal Wifi network and not in a larger "public" type environment that may exist in an Assisted Living facility on a network not fully controlled by the user. I'd also take a look at this document.
If you want to use the device for your dad, you will need to invest in a travel router or some similar device that would enable you to create a secure personal network available in your dad's room. Keep in mind, the facility may also prevent the use of network equipment for security reasons. It's also possible the facility blocks ports needed for the device to work properly. Absent that, there are no solutions or support for this scenario."
Saying all of this, the travel router MAY or may not work, you will need to speak to the assisted living facilities IT or support team to see if this will work for their network setup.