I too had this message (August 2018). The file in which I stored my password prompts became inaccessible. A problem which stopped everything.
Luckily my backup file from a local was still yesterday’s version, and when copied back to main disk, opened OK with Axcrypt.
The only thing I can suggest is to backup your vital stuff before upgrading Axcrypt. Unfortunately, if you’re reading this, it may be too late.