Same issue. Same general start of issue around December 2023, after a Chrome update.
Corporate Macbook, Chrome, NabuCasa URL. IPV6 is completely disabled on all hardware I have control of, and in HA Network settings.
RETRY NOW shows up basically every time I reload, and I have to click it up to 10 times to get back to my dashboard.
No issues when using 192.186.xxx local address with Chrome.
No issues when using Nabu or Local on same machine in Safari.
Any security products on this Corp Macbook or the Corp network?
Any issue with Chrome on other devices other than this one?
iPhone with Chrome app on same corporate network has no issues with Nabu URL.
As far as IT-sec software, there’s a ton loaded on this Macbook, but it’s been generally the same since before the problems arose:
Crowdstrike (Falcon), Zscaler, Okta, JamfDaemon are the main ones.
Got a co-worker’s device you can borrow for a minute? 
Good news everyone. After testing multiple machines and finding it was really only Chrome on my 1 laptop having this issue, I finally nuked it from the hard drive of the Mac (using some scripts I found here to annihilate all settings – a normal re-install does not work).
Upon a clean Chrome install, I haven’t had the issue once on the problematic machine. So give that a try if you run into this.
Im having the same issue. It was originally with Chrome on multiple devices. Now Edge as well. I can click on the Retry Now multiple times and can eventually get in.
Firefox works ok. This is weird.
In the last few days I’ve been having the same issue from multiple ISPs and different devices.
I’ve only tried from Chrome, the error in the console is that the browser is not able to establish the WebSocket connection.
+1
Exactly the same here… using Brave Browser on my Pixel 7 works like a charm.
I’m having the same issue since 2-3 weeks ago. Before that any error like that.
Same issue here, since last week (Microsoft Edge 124.0.2478.51)
I have the same problem since today.
The only difference is that yesterday I updated Chrome to Version 124.0.6367.61 (Official Build) (x86_64)
Sometimes reloading the tab or trying again from the button makes it work fine again
As it turns out - for me at least - the root cause is the Ghostery extension. When I disable that for nabu.casa everything works like a charm. This would also explain why the problem is isolated to Chrome as Chrome is the only place I have Ghostery installed.
I opened a ticket to their support and it’s a known issue that they are working on:
We are looking into an issue which appears to involve a setting in Chromium based browsers (Chrome and Edge). Disabling this option is only a workaround until we find what is causing this on our end.
This can be found by entering chrome://flags/#enable-tls13-kyber or edge://flags/#enable-tls13-kyber and then setting that to disabled.
The other option is to use an alternate browser such as Firefox until it is determined how this can be resolved on our end.
This solved it for me, thanks!
Enabling nabu casa with ghostery also fixed the issue.
Thanks, this solved my issue too.
OMG I wish I could come over there and give you the biggest high-five! I’ve been fighting with this all day long…should have looked here first, but was trying to see if the problem was on my end!
Hmm… replying to my own post… it stopped working after a few days. Even with Ghostery disabled 
Works when disabling the flag as posted by @LookedPath