On Wednesday evening I upgraded the UCG max to 4.1.22 .... and it immediately killed the internet, suggesting I contact my ISP. Prior to that it had been stable for four months or so, apart from the odd bout of reported high latency.

I've since had a 1.5 day saga with the ISP who have "confirmed" and txt me twice that there's an outage at my property which they're trying to fix .... which I found very coincidental but thought the ISP should know.

Anyhow, with time to spare this Good Friday, I fired up an old modem entirely separate to the main Unifi system ... and bingo, the Internet was up, despite the ISP advice.

I then put the UCG Max back into system and audited the full config to see what might have gone wrong on the WAN connection during the upgrade to 4.1.22 and discovered that the Port 5 WAN was set to auto negotiate line speed. I'm unsure if this had been on auto negotiate previously, but I set this to Gbe instead and connected to the internet immediately.

The ISP is currently upgrading its networks and recently allowed DHCP as well as PPPoE on fibre broadband (in preparation for hyperfibre?), and perhaps that going on in the background whilst upgrading the UCG Max confused the WAN line speed setting, but I'm posting this to help anyone in Unifi land who has this same problem ... and save them 1.5 days of system downtime and confusing discussions with their ISP!

AndyTNZ