I apologise if this step was not needed.
In my setup, I have added the tester in Admin > Equipment.
I have added myself as an engineer in Admin > Engineer. I have also told the system that I have that tester, again in Admin > Engineer > Test Equipment
Then when I open a certificate, when I get to the "Boards and Circuits" page, you need to tell it which Engineer did the testing:
View attachment 89213
Click Edit Board, scroll down to this bit:
View attachment 89214
Then when you choose yourself, the tester should appear too:
View attachment 89215
Does that help?