If you encrypt the new file that file will be added in the recent file list.
I think you might clicked the reset button in the sign-in dialog or Stop Securing and remove from list or Remove from list but keep Secured or Clear Recent files option.
If you click the Stop Securing and remove from the list option, AxCrypt decrypts the file and removes it from the recent file list.
If you click the Remove from list but keep Secured option, AxCrypt keeps secured the encrypted file but remove from the list.
If you click the Clear Recent files option, AxCrypt clears all the recent file list.
If you click the Reset button in the sign-in password dialog. That button is used to reset the AxCrypt account data in the locally installed AxCrypt app. That means, it will clear all the local contents cache of the AxCrypt app and restart the app like a freshly installed one.
In the above cases, you can do that, that is the reason you cannot see the encrypted file in a recent file.
if you open/update the previously encrypted file that file is automatically added to the recent file list.
Still, if you are facing any issues, please write an email to firstname.lastname@example.org with some more information about the issue.