Updates should show up in the App Store, but there very well could be times when an update wouldn’t show if it wasn’t compatible with your current OS. For example, I believe FCPX 10.4 requires OS 10.13. So it’s one of those things where you kind of have to keep an eye on both. In my situation, I’m in a corporate environment that has a desktop image managed at the IT level well-beyond my control. So my App Store updates are turned off. That means I have to occasionally manually check for updates. But I do try and stay up-to-date through a few industry newsletters and generally have an idea when something has popped up.
Having said that, nothing is foolproof. For example, I’ve stayed on top of updates, but somewhere missed one of the more important tid-bits of information–that you’ve found out the hard way. One of those updates left behind older FCPX projects. When they converted to libraries I think in 10.1(?). Anyway, it was a rude awakening. Thankfully Apple provided that older trial and I spent quite a bit of time trying to future-proof older projects by converting them with the trial before it ran out.
Which brings up a good point about archiving older projects. It’s one thing to move forward via the latest updates, but another to keep an eye on the past in terms of being able to open older projects. And Apple (unfortunately) hasn’t done us too many favors in that regard. For example, I’ve got a ton of stuff in FCP7. Which means to future proof those projects, I probably should, at the very least, export an XML of each project in the hopes of being able to get most of it recovered in PPro (or using the 7toX app)–should I ever need to get ahold of one of those older/aging projects. I’ve got one more machine in the shop that will still run FCP7 before IT takes that one away and upgrades it. I believe it’s 10.13 that goes full 64-bit and thus leaves behind FCP7.
One eye in the future and one eye in the past with a lot of troubleshooting in-between. It’s what we do. Good to hear you’ve been able to get yourself back up and running (or limping along). ☺
— Joby.