For the above error, I would make sure database ‘root’ actually exists on your dev server. You can get more information about the error in the vdp.log file in <DENODO_HOME>/logs/vdp.
I would also make sure there is enough free disk space.
For more details, refer to similar community questions.
1) [Unable to connect Denodo Virtual Data port](https://community.denodo.com/answers/question/details?questionId=90670000000XcYWAA0&title=Unable+to+connect+Denodo++Virtual+Data+port)
2) [Database connection issue in denodo6](https://community.denodo.com/answers/question/details?questionId=90670000000XcWLAA0&title=Database+connection+issue+in+denodo6)
Hope this helps!