It is possible that the stand riser slide mechanism is stuck.
* Turn the S3225QS off
* Lay a soft towel on the desk
* Gently lay the S3225QS panel down on the towel
* Disconnect the stand riser and base from the rear of the S3225QS
* Stand the stand riser up on the desk
* Push down on the square bracket until you fell it slide down the stand riser. This might take a little effort to move it
* Once done, reassemble and try to lower with the panel attached

Thanks for the reply.

This actually took an unbelievable amount of two handed pressure to move it to the lowest position.  But unfortunately the return spring is so strong, the screen forcefully goes back up to the top on its own.

"the screen forcefully goes back up to the top on its own."
I cannot find any way to "adjust" the spring.

I would not dream of using the ridiculous amount of force required to push the monitor down, because even then it just will not stay down and shoots straight back up.

My workaround has been to put a short wooden wedge in the groove and as the monitor is only 2 months old, am trying to get Dell who I purchased it from to replace the stand.  But I’m being given the run around as firstly they say I need to purchase a new stand, then another says if it was the monitor screen at fault they would replace the monitor but can’t do the stand and now I’m with customer service who appear to only work part time, as I have to try them yet again tomorrow.

I just bought this same monitor and have exactly the same problem. The height is locked at the maximum and I want the minimum. I have found no solution and am reluctant to force it anymore that I have tried. It is a ridiculous pressure. There much be a lock somewhere?

In my block of wood solution above I firstly had to remove the screen from the stand, but still waiting for Dell to respond with a new stand.  However, as you have the same problem it looks like a new stand will not solve the problem.

I just installed this monitor, and I cannot lower it. No matter what I do it does not move and is stuck on the higher position

@DELL-ChrisM2​ this did not work. Monitor is stuck on higher position, and I need to lower it