Okay, here's a head-scratcher and no mistake.
I have a 15" 2016 Macbook Pro (a Macbook Pro 13,3). A long time ago, I ran a firmware update on this Mac. All well and good. The Mac came with Firmware version 4126.96.36.199.0 and the current version from Apple is 4188.8.131.52.0.
The Mac went in last year for warranty service, and they replaced the logic board. The logic board they put in is back to Firmware 4184.108.40.206.0, the old version.
But here's the thing: I can't update to the new version! App Store doesn't see it as an update. It can't be installed, I suspect because somehow the update logs or something "remember" that I've already run the update. And without the firmware update, I can't upgrade past macOS High Sierra (the 4220.127.116.11.0 firmware is required for any operating systems beyond High Sierra).
It's a real pickle. I can't find a standalone firmware updater anywhere, not even on my Apple Developer account. Any ideas?