HDMI Input on 7700 AIO. Display BIST button no effect. Is Dell-On-Screen-Display-Application_0YDH6_WIN_1.0.1.0_A01_03 required?

PROBLEM: Cannot use HDMI INPUT port. The Display Built-In Self-Test Button is supposed to select either the 7700 AIO as the source for the built-in monitor or an external HDMI source.  Source selection is accomplished by pressing the button multiple times. There is no on-screen display or other user interface. THE PROBLEM IS THAT THIS BUTTON APPEARS TO DO NOTHING.  Therefore the external HDMI source cannot be selected.  Repeated button pushing finally produced a blank screen which did not show the HDMI source that was plugged in to the HDMI port. Button is very difficult to push.  I finally used a 3.5mm male plug as a tool with which to attempt to depress the button.  Very frustrating dealing with this button on the bottom of the monitor.

This case from 2021 is relevant in locating this hard-to-see button: "Using HDMI INPUT on 7700 AIO."

https://www.dell.com/community/en/conversations/inspiron-desktops/using-the-hdmi-input-on-a-dell-7700-all-in-one/647f9496f4ccf8a8de6e4e23

We now know that the hard-to-see Display Built-In Self-Test Button (button 2) is next to the Power button. (See image at end of post).

Info About Dell OSD (On-Screen_Display) App in Dell AIO Computers is a relevant technical note (Article Number 000132150). https://www.dell.com/support/kbdoc/en-us/000132150/information-about-the-dell-on-screen-display-application-seen-on-optiplex-aio-systems

Notes from this article:

I have downloaded the OSD app, but it appears to be for Dell Optiplex AIOs.  I hvae not yet attempted to use this app.  Is it applicable to my problem?

Thank you for any help!