Hello L.M. Roos,
AxCrypt can encrypt most of the file types. AxCrypt will not encrypt any system, hidden files and operating system installed drives/folder. So please avoid securing that kind of folders/file(s). Also above file types, AxCrypt will not encrypt due to security reasons.
If you are receiving the warning dialog frequently, please click the Don’t show this again option. After that, you never see this kind of warning.
still, you are facing any issue, please provide more information about the issue and write a mail to firstname.lastname@example.org .