DropBox API auth error - {".tag" = "expired_access_token"}

Even if you've uninstalled the app, the client may still be saved locally since that's persisted in the iOS keychain. And if you've disconnected the app via the Dropbox web site, the SDK won't yet know that the connection has been revoked on the server until you attempt an actual API call, like listFolder, at which point you'll get an authorization error.

You can just call authorizeFromControllerV2 again to prompt the user to re-authorize the app. Or, if you do want to explicitly remove the local client, you can call unlinkClients at any time.

That is not a solution.

I can't write temporary code. I need to have normal way to verify if dbClient is valid object or not.

What if user want to connect another account.

There must be better approach.

I'm not sure understand what you mean what you mean by "temporary code". The authorization flow with authorizeFromControllerV2 works effectively the same as it did with authorizeFromController, since the SDK handles the refresh flow for you. Just like with authorizeFromController, you can just process the authorization flow with authorizeFromControllerV2 and let the SDK handle the access token details for you. You would check and use authorizedClient the same way in both cases. (While authorizeFromControllerV2 uses short-lived tokens in its implementation, it works the same way for the app's code as before, since it maintains long-term access using refresh tokens automatically just like the SDK previously maintained long-term access using long-lived access tokens from authorizeFromController.)

If you want to have the user switch to a different account, you can call authorizeFromControllerV2 again and it will replace the authorizedClient.

I recommend following the instructions in the current documentation. If something isn't working as expected/documented, please show both the steps/code you're using, as well as the full unexpected error/output.

OK. I will try to see if it works also for other users. Thanks for help