What could be causing the 'Check Charging System' warning on my 2004 F150?

So, here’s the deal: my 2004 5.4 Lariat had a dead battery, so I swapped in a new battery and a new alternator. But now, about 30 seconds after starting it up, I’m getting this ‘check charging system’ message with the battery light on. Pressing reset gets rid of the message, but the battery light sticks around. It’ll stay off for a bit, but then after about 10 minutes, the warning pops up again.

Now, the truck seems to crank and run just fine, but this warning is bugging me.

Any ideas on how to fix it?