The basic idea of a hash function is that you can’t invert it easily. Depending on the hash and energy and resources, you might want to find a collision that solves your hash (two different inputs can give the same hash output).
What you want to do is to reset the updater secret to something you know. There is a code snippet that you can use to create a new one:
It gives you the updater secret and the hash-value to put into the config file.
Other way, just use the updater on the command line (same linked discussion, just the post before).