How to update a unifi controller to allow it to upgrade properly

update-unifi-controller

Look for any expireed GPG keys:

root@vm100ubuntu:~# apt-key list
/etc/apt/trusted.gpg
--------------------
pub   rsa4096 2016-01-11 [SC] [expired: 2020-01-05]
      0C49 F373 0359 A145 1858  5931 BC71 1F9B A157 03C6
uid           [ expired] MongoDB 3.4 Release Signing Key <packaging@mongodb.com>

Any that are expired need to be replaced:

root@vm100ubuntu:~# sudo apt-key adv --keyserver hkp://keyserver.ubuntu.com:80 --recv-keys 0C49F3730359A14518585931BC711F9BA15703C6
Executing: /tmp/apt-key-gpghome.zNjIXKCE0q/gpg.1.sh --keyserver hkp://keyserver.ubuntu.com:80 --recv-keys 0C49F3730359A14518585931BC711F9BA15703C6
gpg: key BC711F9BA15703C6: "MongoDB 3.4 Release Signing Key <packaging@mongodb.com>" 1 new signature
gpg: Total number processed: 1
gpg:         new signatures: 1

Then apt-get the update and allow version bumps:

apt-get update --allow-releaseinfo-change
apt-get upgrade