Unfortunately, it is not possible to recover the KEY file directly from the SAT or in any other way. But here is an alternative.
In case of loss, we recommend you to revoke your e.firma immediately to prevent misuse, especially if you think someone else might have access to your KEY file and its password. This step is crucial to protect your identity and your documents.
To continue using your Mifiel e.firma, you will need to obtain a new one at the SAT. This process is similar to the first time you obtained it and, although it may seem complicated, it is quite simple. You only need to schedule an appointment at the SAT under the category "e.firma renewal or revocation" and attend on time.
Once you obtain your new e.firma, you will be able to resume signing contracts and other documents in Mifiel using it. In addition, we recommend that you keep a backup copy of your new CER and KEY files and write down its password in a safe place.