Magic Keyboard will not reconnect after change of batteries

I'm working on my parents 2015 OS X Big Sur. Computer notice said to change batteries on Magic Keyboard, so I did. Fresh batteries out of an unopened box. Now, I receive a message from Bluetooth Keyboard Setup "There isn't a keyboard connected." After exactly 1hour, I still get the same message. The wireless mouse works, but the wireless keyboard will not connect.

What I've tried:

Re-started the computer and router (3X's)

Internet indicator shows connected

Tried the pea size piece of aluminum foil in the battery compartment

No other keyboard available to use or test

Moved router and modem closer together - moved them apart.

I have tried push the on/off button once, I have tried pushing it 2x's quickly, I have held it down for 3 seconds, 5 seconds...all to no avail...and no green light I keep reading about.

The message also states, "Make sure you keyboard is "discoverable." I will assume that means "on." I've read about a green light, but do not see anywhere on the keyboard for a green light. The on/off button (NOT a switch) is located at the opposite end of the battery tube, and is a simple push button activation. There are no ports for direct connection to the computer.

Any suggestions?