If you had a free account, it's already too late - everything has been deleted.
If you had a paid account, you should still be able to
- log in at their site https://www.boxcryptor.com/app/
- export your key as a *.bckey file
Using this file and your boxcryptor password you can still decrypt your file
on Windows:
- start the boxcryptor app, but do no log in
- instead click the three dots in the upper right corner, and chose "local account"
- drag and drop your *.bckey file into the app
- type in your password
now the app is running as before, and decrypting your cloud files and
serving them as a virtual drive. You can keep using it, or just
copy the files over to another storage location.
On MacOS:
- double click the *.bckey file in finder - this will start the app
- type in your password
now the app is running as before, and decrypting your cloud files and
mounting them as /Users/USERNAME/Library/CloudStorage/ You can keep using the app, or just
copy the files over to another storage location.