You should search and ask here:
http://www.artlantis.com/_forums/index.php
A screenshot of the message that you get would help.
5 does open 4.1 files fine... I haven't tried a 4.0 file. (4.1 is a free upgrade... sp ,maybe you need to install that, convert to 4.1 and then try 5.1?)
One of the forum moderators
AC 28 USA and earlier • macOS Sequoia 15.2, MacBook Pro M2 Max 12CPU/30GPU cores, 32GB