The UD Google Nest Device Access is stuck in "Commercial Testing" status until a number of authentication and API tests can be completed and verified. Until all this can be done, we are limited to 10 users, which we hit several weeks ago. Accordingly, I have taken the Nest Plugin off the Plugin Store List (marked "Inactive"). If and when the various battery of tests are completed, we can move it into the next phase of "testing" (not production yet), requiring even more rounds of verification testing, including a paid 3rd party security audit, evidently. But we should get a higher user limit at that time. 

Also, remember that you can use the Nest SDM plugin with your own personal Device Access project created in a private Google Developer Sandbox. Instructions for that are in the Instructions and Release notes.