I was able to reproduce your scenario. The error **Unable to establish connection: Cannot open database** could have occurred due to various reasons such as:
* The database ‘MAXXPHASE’ no longer exists in Microsoft SQL Server.
* The user connecting does not have the necessary privileges to connect to the particular database.
I’d suggest you to try using the valid database name in the connection URI and provide the correct login details.
For more details, you can have a look at a similar Community Q&A [here](https://community.denodo.com/answers/question/details?questionId=9060g00000009zpAAA&title=Unable+to+connect+to+Microsoft+SQL+Server+2012).
Hope this helps!