Not a network as such. Our computers are in the same property but in different rooms.
The problem experienced happens regardless of where the file is located, that is on the local computer a Windows 10 account is logged on to or on another homegroup computer.
I wasn’t asking about conversion between different Axcrypt versions, rather considering the implications of having no problem when opening newly created Axcrypt files (i.e. those created in the current AxCrypt version).
As you have been unsuccessful in recreating the problem I’ll experiment with decrypting a file created with old Axcrypt and encrypting with new Axcrypt. Failing that I’ll copy and paste the contents into a brand new Excel file and try encrypting that.