When you get the error message saying that the shared location path is not valid, it typically means that the expected files are not being seen in that location. This could be because of permissions preventing it from seeing them or it could be that the wrong folder is being used for the shared location.
I suspect that the error message is seen when the Remote Repackager setup is unable to find the Shared AdminStudio.ini file.
The AdminStudio Shared folder is expected to contain the following files at its root:
EA_Default.xml
isolationconfig.ini
isolationconfiguration.xml
isrepackager.context.ini
isrepackager.ini
issnapshot.ini
PostReplication.sql
PreReplication.sql
Shared AdminStudio.ini
In addition to the above listed files, there are two subfolders:
ConflictSolver
Help
Also, if you are an AdminStudio Enterprise Edition customer making use of the AdminStudio Platform API, a file will be created at the root named PlatformSettings.xml
And typically customers will also create their own subfolders in the AdminStudio Shared folder to keep and share things such as templates, custom actions and merge modules.
One other note: There are actually two folders named AdminStudio Shared (I know, awesome, right? The more the merrier) One of them is located at C:\Program Files (x86)\AdminStudio\2013\AdminStudio Shared\ and is NOT the folder that the Remote Repackager setup is looking for.
The folder that the Remote Repackager setup is looking for is installed (by default) to C:\Program Files (x86)\AdminStudio Shared\ and should contain the files listed above.
I hope this helps,
-Evan