I can’t be 100% sure about what your user name is, but I’m guessing it’s something like “firstname.lastname@example.org”. If this is correct, you may want to start by updating AxCrypt to the most recent version from https://www.axcrypt.net/ .
Regardless, you should be aware that saving under a new name from withing Excel can indeed lose you the changes made, since we don’t do anything with files saved under a different name. If you save it in a different location, we have no idea about that either – we literally can’t see what you save where from Excel, except in theory if it’s to one of the folders monitored by AxCrypt.
If you want to save a copy, ensure you do so in a place you know where it is, and also that you subsequently encrypt it, or save it to a secured folder location where AxCrypt will see that it needs encryption and will do so when you exit or you click the red ‘clean’ broom icon.