Hmm, might tag @Mattches for ideas. I mean, there’s the potential of just telling you to leave the sync chain and try making a new one completely or something, just to see if that resolves. Issue is not a lot of User side troubleshooting and fixing to do that I’m aware of.
I also know had been an issue for someone else, at Error when adding tablet using QR/Code word
If everything is up to date, you’re generating the code same day, etc then I’m not sure why it would be showing a failed sync.