To reproduce, use the ADS install at 10.168.11.57 and use the database named GTWMDB which I have detached.

1. Open SQL Server DBA Tool - Storage Manager

2. Go to the Databases Tab

3. Right Click on any database and select Attach Database

4. Add a file

5. Click the Alter and ADS does not close the Alter Dialog so it seems as if the Alter was not successful.

6. if you refresh the Storage Manager, you will see the the Database is there.

Ivan points out that there may be Warnings preventing the dialog from closing, but we don't have a Warnings tab.