All Microsoft Serial/PS2 devices require a true Microsoft adapter (or one wired as one, there are other topics here about it) so using any old generic adapter has a 50%+ failure rate.
If the mouse or trackball is already PS2 then you def need a specific adapter to convert back to Serial. I have a few MS serial/ps2 mice and most of them came with an adapter.
My MS Intellimouse Serial/PS2 says same thing as that box picture and included the PS2 to Serial adapter and it works on all the MS Serial/PS2 that are PS2 native,
conversely have MS serial to PS2 adapters and they work on all wired serial. If wired for Logitech or Mouse Systems it generally will not work with a MS device.
So you need to search out the wiring of MS adapter and match it. Good place to start: Serial port with PS2 adapter.
Also you want to use the DOS Intellimouse driver, no Cute Mouse or Logitech or other...just MHO

Thanks. I was just reading through the threads and discovered this one where they mention the grey 68666 labelled adapter:

Microsoft PS/2 to serial pinout?

Is this the one you use?

https://www.ebay.com/itm/383004472954

I also found the intellimouse floppy winimage in the drivers section.

http://vogonsdrivers.com/getfile.php?fileid=2089&menustate=0

The adapter I was using is green and is most likely for a logitech mouse.

Good search ! Yes that was the topic I actually was thinking of. Yes think all the green ones are Logitech.
My MS adapter does not have the number on it, it came with sealed boxed MS Mouse Serial/PS2 with ps2 cable and the adapter to serial. It basically looks like a generic grey one but was the included one.
for reference: original MS archive of the webpage for your trackball: http://web.archive.org/web/20000412023900/htt … e/trackball.htm
added: If I have time will check the pinouts of my adapter.

The green adapter came with this logitech mouse which seems to be able to reduce the serial to 5v according to the pinout.

It might be a windows only mouse because I haven't had any luck getting it to work in dos/win 3.1

What version Mouse is it ? on the mouse back should be a label with a model number.

It is model m-caa42, and this one is a 2 button Logitech serial mouse.

Jester wrote on 2023-09-10, 18:37:

78BA4810-C305-4439-9040-DC7E535FDD9B.jpeg

It is model m-caa42, and this one is a 2 button Logitech serial mouse.

Those are common and should work on serial or PS/2 IF you have the proper PS2 to serial adapter iirc.
You should use Logitechs DOS mouse driver from Mouseware 8 as it has good support for both serial and ps2.
Have you had any luck with any mouse on your COM ports ? You might want to check your adapter setting and make sure they are standard Com1-IRQ4- 3F8 and Com2-IRQ3-2F8....