Error: Sorry, this file type is not permitted for security reasons.
The latest WordPress version 4.7.1 (also affects version 4.6.2) introduced a mime type bug that prevents users from uploading CSV files. It will probably be fixed on the next release because this bug affected not only WordPress and our Gravity Forms Import Entries plugin, but several other plugins too.
Meanwhile, some WordPress users are suggesting installing the Disable Real MIME Check to bypass this problem and be able to import the CSV files again.
The GravityView team is very sorry for the inconvenience.