Please just read the documentation. It’s been created for a reason…

https://aximmetry.com/learn/virtual-production-workflow/preparation-of-the-production-environment-phase-i/setting-up-inputs-outputs-for-virtual-production/video/srt/srt/

The same version 4.2, on a second computer, I find SRT available ?!

Did you read the documentation I linked to? The SRT output isn’t there by default, so you need to add it (as described in the documentation). If it’s available on one computer it means that you (or someone else) added the SRT output. 

I sure read it

. This is a picture from my computer that appears on it by default and I used it. As for the picture above, it is from my laptop. I updated the same version and it does not appear. This is my question.

Ah, you didn’t mention this was for Aximmetry Eye. Those SRT connections gets created automatically when you enable Aximmetry Eye on a computer. You’ve done that on one computer but not on your laptop. Hence the difference. Again, this is clearly explained in the documentation. Easiest way is do use google to search the documentation. This was the top result when I googled Aximmetry Eye documentation: 

https://aximmetry.com/learn/virtual-production-workflow/preparation-of-the-production-environment-phase-i/starting-with-aximmetry/aximmetry-eye/what-is-aximmetry-eye-and-how-to-use-it/