My phone just says “update requested…) and isn’t doing anything else.

Isaacayers12 Said:

"It won’t download the update and I’m plugged into a charger and on a good Wi-Fi network."

-------

Updating an iPhone 12 Pro Max:

When it comes to updating an iPhone, aside from WiFi or a Computer, your only other option is to use Cellular. So, try update using Cellular. If of not success, try this once more, this time using a computer...

See my User Tips:

• Update your iPhone Using a Computer - User Tip
• Use an iPhone 12 or later, that is using 5G, in order to update over Cellular - User Tip