EFS won’t decrypt and doesn’t ask for certificate or keys

As administrator of a very small network, I intend to give access to my files to all users. In my attempts to decrypt the folder and files, there is no check in the box “encrypt contents to ensure data”. Then I uncheck the read only box, let it finish, and then try again with the decryption it says “The process cannot access the file because it is being used by another person” During this time, there is no one accessing the folder/files as I have turned off all networking as well as wireless and internet access. Of course, I backed up the entire encrypted directory before I started.