1. Is this a client library issue or a product issue?
   Client library issue with samples.

2. Did someone already solve this?
   no

3. Do you have a support contract?
   No - Internal request

Issue:
The region tags used in the samples (generated and handwritten) are using the invalid product prefix notebooks.
There are 67 region tags that need to be updated based on this search https://github.com/search?q=repo%3Agoogleapis%2Fgoogle-cloud-node+%5BSTART+notebooks&type=code&p=4

The impact of this is that these samples don't show up correctly in devrelservices and so wouldn't get included in Sample Browser.

Resolution:
The region tags should have their product prefix updated to aiplatformnotebooks, the correct prefix for Vertex AI Workbench.