How to import a key to an e-token?

Question

Cryptography

Received a digital signature in the form of a Key-6 file (.dat) and a certificate (public key .cer).
I'm trying to import a key to Aladdin's e-token through their PKI client version 5.1. The certificate is imported, but the Key-6 key file is not - it does not see its token. How to fix?
The most annoying thing is that two years ago I did all this and everything worked, but now I forgot everything.