Hello,
Thank you for using Google Groups!
Before we begin, for the purpose of context, what kind of error is the one you are referring to? Also, when you mentioned that you "updated gcloud and other things", would you be able to clarify how you did this step? This will help isolate the issue as well as understand the steps that have been taken so far.
Additionally, as you are using Maven, I was able to find a guide on how to use Apache Maven + the App engine Plugin on Google App Engine: standard
here. There are also instructions on how to set up Maven provided there. You may feel free to follow the steps mentioned in the link provided above.
As for the gcloud aspect of the issue mentioned, you may try a clean install of the SDK to determine if this would resolve the issue. For installing the SDK, you can see the official documentation
here on how to do it for the latest Cloud SDK. The instructions vary on the OS that you are using. However, this step will ensure you are getting the most current version available.