This may be a dumb question, but if you go to the About Sync3 section, your original non-nav VIN is displayed, right?. I’m saying this because I’m not sure if you can (or even should) change the VIN to enable a map upgrade. Even if possible, I would not do that.
In the meantime, you can check this thread → Tutorial: 2020 North America 2.20 Map Installation (Stand-Alone without Reformat) with Updated NAV_Voice 06/21/2021
You can install more current maps with Syn3updater and that thread as a guide, since you have a MY20 unit you can’t reformat it, but you can use autoinstall as described.