Hi, I'm getting token expiry every few days. I don't seem to be able to renew the token from my watch which is leaving me very worried I'll be left stranded at some point. I don't carry my mobile and it is an older model S so Bluetooth isn't a backup.
What can be done to make sure the app doesn't leave me in the middle of no where?
The token on the watch is only valid for 8 hours before it needs to be renewed. This is done with a request to Tesla's auth server using a one-time refresh token. Tesla takes a very strict approach to this request, giving the watch no way to retry the token renewal process if it fails or the refresh token has already been used. To mitigate some of the risk, the watch sends a status request to Tesla just before sending the token update request. This is to ensure that the watch is connected to a working mobile or wifi. Even with this approach, the token update can fail and the watch has no option but to ask you to sign in again on the phone app. This is more likely to happen with a watch that uses LTE than with a watch connected to a phone, simply because of the more unreliable connection. Without a valid token, Tesla will not accept further commands.
I would not recommend using the watch as the only option. On newer car models with BLE and NFC, it is different because of the built-in backup this offers.
The only thing I can suggest as a preliminary rule is that you open the app in places with a good connection before you know that you will be using the app without a backup for the next 8 hours. This requires that you have not opened the app for 8 hours so that you know the app will update the token.
PS! Just to avoid confusion. As far as I remember, the watch does not use the term "Token Expired". The app will say "Token renewal failed!" or something like that. If you've seen this on the phone app, this refers to the first initial token after a valid phone login. This token is also valid for 8 hours before it expires, but if this token has already been transferred to the watch, the watch will renew it by itself without the help of the phone.
Sorry for the long answer here, but it's hard to give a short answer other than the app can't be trusted 100% in your case. In any case, you now know why.
