Hi
Without the masterkey file you can’t open your vault. If you do have a recovery key for your vault, you can try and recreate the masterkey file.
See here: Recover masterkey file with recovery key? - #4 by tobihagemann
If you don’t have the original masterkey file and do not have the recovery key, and if you do not have a backup anywhere, you will not be able to open your vault and decrypt files anymore.