The development of the Protect Files app has been ceased, this means that there will be no new version of this application.
Apimac recommends using Disk Utility to create encrypted disks. Online there are several tutorials on creating encrypted disks on the Mac, one of these is this one:
How to Create a Encrypted Dmg File (Mac)
If instead there is the need to extract data from an encrypted space without using the application, you can follow this simple guide (of course you will need to have the password, otherwise you can not access the encrypted files):
This is just one of many tutorials available, choose yourself which best suits your needs such as simplicity or accuracy of the steps.
Related solutions:
How to access your data without launching an encrypted space