The 'Check for Update' feature in Android has been a real piece of work for some time now. It was announced in September that this was being reworked to actually pull in new updates rather than just seeing if one was available in your area, but the rollout was delayed due to a bug with Google Play Services.
Thankfully, it would appear that things are now working as they were intended.
A few Redditors recently shared that the Check for Update button wasn't doing anything with Play Services v11, but updating to v12.2.09 actually started to pull in the latest February security patch that Google just released.
Play Services v12 is currently limited to those enrolled in the Google Play Services beta, and if you're not currently enrolled in this, you can do so here and get access to the latest beta version when the next update drops.
Alternatively, you can skip the line and go straight to downloading the APK file for it. Some users have reported that they've gone through this process successfully, but if you're not careful, you could end up breaking Play Services and needing to factory reset your phone.
There's no exact timeframe as to when v12 of Play Services will be made available for everyone, but seeing as how it's already in a beta form, I'd expect it to roll out to the general public within a matter of days.
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