Vision Client Launcher HTTPResponseException 503

We have one laptop on our network that is failing to launch Ignition using the Vision Client launcher. The settings appear to be identical to other machines that are working. One difference is the laptop that doesn't work is running Windows 11. We tried disabling Windows firewall but that didn't help.
There is no issue with accessing the gateway webpage.
The log is showing 'Download failed for synthetica-addons-3.4.1.jar' (see screenshot). Has anyone seen this before?

HTTP503 Error

What Ignition version is this?

The only case Ignition itself will return a 503 is if you hit a certain concurrency threshold for incoming network requests, and you have to be in a specific band of Ignition versions to be affected for this launching code path; if you're on a new enough version there's a flag you can change.

Version: 8.1.20

Can you get a Wireshark capture?

I would think this means one of two things:

  1. the gateway isn't in the "Running" state yet
  2. you have a network appliance in the middle that is returning this HTTP 503

I'm not sure the route concurrency stuff Paul is alluding to affects the JAR download servlet.

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I think we tracked it down. Looks like there's been a change in our network security that is now blocking .jar file downloads. The computers that were able to launch Vision had downloaded the files to the .ignition cache before the change, but this new machine wasn't able to. I'll confirm tomorrow with IT, but deleting the .ignition cache on one of the working machines and attempting to re-download recreated a similar error.