Pop up on Dell S2721QSA

Just yesterday a pop-up screen started flashing on the bottom right of my Dell monitor. It appears even when I turn off my desktop, so I’m guessing it originates from my monitor, rather than my desktop.

It’s a dark rectangle with a black bar across the top, and gray beneath the bar.

In the black bar it reads: Dell 27 Monitor

In the gray beneath the bar it says: Select option:

Below that are 5 images:

The first image is a padlock with a square below the padlock filled with three horizontal lines (this symbol is highlighted in blue);

The second symbol is a padlock with below it a circle with a line pointing up;

The third symbol is a padlock with below it both the square + the circle symbol;

The fourth symbol is a vertical line;

 The fifth symbol is a monitor with below it a wrench criss-crossed with, possibly, a screwdriver.

Outside this pop-up, below it, are 4 separate symbols: an arrowhead pointing left, one pointing right, a check mark, and an ‘X’

Like I said, this pop-up just started appearing yesterday, and won’t go away. I’ve tried turning off the screen, turning off the CPU. They keep reappearing.