Thank you for your reply.
I tried a few other things.
First I moved the GX20 to be behind the AmpliFi. So, the AmpliFi was the internet gateway. The Meraki Go app could see the GX20 on the network.
Result: Still no reboot.
Conclusion: Bridge mode is not the issue.
Second, my ISP provides some filtering capability that can be configured on the web. None of that appears to block Cisco traffic, but I temporarily disabled the filtering completely.
Result: Still no reboot.
Conclusion: ISP filtering is not the issue. However, I have contacted my ISP to check if any web sites or ports are blocked globally on their side.
Third, I notice that in the app there is Hostname assigned. It looks like this format:
<organization name>-appliance-<some kind of random characters>.dynamic-m.com
I assume this is to handle Dynamic IPs.
Result: Trying to get to his web site fails. Correction: It loads the GX20 configuration page.
Conclusion: Not sure if I am meant to see the contents of this hyperlink. Correction: It loads the GX20 configuration page.