It’s a little hard tell from your screen shot, but the reason only “Decrypt” is offered, is because the file in question is already Encrypted. I think you got confused about what file you selected to “Stop securing and remove from list”. Try again, and keep track of exactly what file you’re working with and I think you’ll find that it works as expected – as long as the file is not in a Secured folder!
If the file in fact is located in a folder designated as “Secured”, it will soon be re-encrypted again since those folders are monitored for unencrypted files and will encrypt them when you sign out, or click the “Broom” clean up icon.
AxCrypt uses a single sign on method of password use. There is only one password for all encryption and decryption operations, and AxCrypt will stay signed in, and use the same password until signed out. That’s why you’re not prompted for a password when encrypting new files. This is also to reduce the risk that users get confused about what password was used to encrypt what files, or worse mistype the password and not detect it until much later.