Google is upgrading more and more businesses to the new Google business local dashboard and during that process is running into issues with old listings being duplicate.
Google is sending out emails to business owners with issues with instructions on how to repair the duplicate issue and move forward with the upgrade.
Jade Wang from Google posted in the Google Business Help forums a snippet of the email and then in detail described the issues and how to address them.
The email reads:
We'd like to inform you that Google Places no longer accommodates more than one authorized owner per business location. Your account contains one or more listings that have been identified as duplicates of other listings and as a result, some of the information you provide will not be shown to Google users anymore...
There are two issues where this can be triggered:
(1) Your account and another account that you don't control became verified for the same business using the old Places dashboard.
(2) You may have verified the page multiple times using accounts you control.
In each case, Jade describes how to repair the issue so you can continue with your upgrade.
For more details see the Google Business Help thread for those details.
Forum discussion at Google Business Help.