In my replays the standard six instruments does not work, why?

I am new here at X-plane, but I have flown with MS simulator 3 or 4 I think it was, and later a lot with 2004 and FSX. I am also new in designing an aircraft. Even if I was working in the design department at SAAB around 1970 writing software for the 37 Viggen.

I have designed a litte twoseater, the same as I flew when I took my pilot licence. It flies nicely, and all instruments are working. But now I intended to test it in more detail. And I expected to use the replay function to repeat and look at details.

But when I look at a replay the standard six instruments does not move. Some other, for example oil pressure and temperature, they work. And when I repeat some of my flights with the X-plane Cessna 172 all instruments are working also in the replays.

Can anyone here tell me what error I have done, and how to correct it?