Does the windows user you are trying to access the fileshare as have SQL server access to the filetable database? Windows share permissions don't apply to filestream shares so, make sure you have permissions in the SQL database.
The other things you need to check to make sure you have access are the setting in configuration manager to ensure that Transact-SQL access is enabled as well as file I/O access (you can also set here whether clients can connect to the share remotely too).
To access these settings, open SQL Server configuration manager, in SQL server services, right click on the SQL Server Service for your instance and select properties, on the filestream tab you will see the options.
The next place you need to check for settings (yes, you have to enable this feature in 3 separate places!) is the level of access on the SQL server itself.
Open SQL Server Management Studio, connect to your SQL instance and right click on your server and select properties. Click on the advanced section and there is a section for filestream, you need to select full access enabled if you want to use filetable.
I actually found this article after typing all of that which explains how to enable the pre-requisites for filetables:
Enable the Prerequisites for FileTable
Hope this helps.