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Here is the direct link for the Petri script:https://metis.fi/en/2018/02/unifi-on-gcp/Take note of Step 5 about setting up the controller. There are some settings to change on the new controller after you restore it and then you make the same changes to your current controller so it will tell your devices to go to the new IP.As far as the certificate not working, there are some logs that can be reviewed, or try posting with that specific question on his site. I just deployed a new VM for my controller in the past 2 weeks and my certificate didn't work either. But I use the unifi.ubnt.com site to typically access mine so I'm not that concerned about it. But I should find out what it causing it.
The easiest way is to use some scripts that another Unifi user maintains that can be found here:https://community.ubnt.com/t5/UniFi-Wireless/UniFi...Just follow the instructions on the page and you are good to go.
Are you using Ubuntu 18.04? If so, the version of MongoDB that comes with it is not supported with current Unifi versions. The Unifi forums have workarounds for downgrading Mongo.If you are using an earlier version and port 8443 is not open, double check the firewall rules and also check the status of the unifi service with this command service unifi statusYou can also check the last several lines (30 in this case) of the Unifi server logs to see if it tells you if it can't startsudo tail /var/log/unifi/server.log -n30
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