Can confirm, let them know after the postings here:

This issue does indeed look to be our end, though we will need to escalate this internally to our Network Operation Centre. I will raise a query with them and get back to you as updates are made available.

It has been broken on and off for a few years now.

Would be nice if they at least acknowledged an issue publicly.

In reply to a post by NICK_ADSL_UK:

It has been broken on and off for a few years now.

I've never had weird issues like this - mine has thankfully just worked since the day it was enabled. Problem now though for me is I have v6 (only) servers and devices now which I can't communicate with.

Indeed - I was thinking that last night.

At one point support where trying to make me jump through the diagnostic hoops which was flatly rejected on my part!

Maybe a couple of 1 start trust pilot reviews will prompt them into action!

I received an email this morning. They fault has been logged under their service alerts now: https://servicealerts.zen.co.uk/active/5/8543

Appears there been an update - things appear to be working again for me at least but haven't had a chance to test a number of sites and services.

And as of midnight last night its even more broken with many v6 networks now no longer reachable

Yes, routing has failed again. I tried reporting it via Zen's online chat but they responded that IPv6 issues can be handled only via email with a 2-day target response time. They then suggested that IPv6 isn't enabled on my account, despite it having worked on my account for years.

Not an impressive response.

It's really bad today. I had a lot of stuff running extremely slowly when trying to do anything network. It's because some networks (including google when I tried just now) are not reachable. So because there is a working ipv6 network it has to time out every single try before dropping back to ipv4 making things extremely painful.

I disabled ipv6 for the first time in a long time!