It's a bit hidden - once you're logged into the Navigraph website, go to navigraph[dot]com/account (or Your Account->Dashboard), there should be a "Get a Navigation Data subscription" option. Should be ~30€ /yr.
When you sub to navigraph, you can use the navigraph hub to update the navdata for the sim. BATC will then read the navigraph navdata over the sim's default.
That is almost certainly messing with the updater. You're actually 3 updates behind as they've released .2225 (which included the sound fixes) and .2260 before this. Remove yourself from that branch (leave the text field blank) and you'll get the latest update