Saab transmission problems

My 1996 Saab 900S manual transmission shifts into reverse position but nothing happens when I let out the clutch. Is something wrong with the transmission or is it something else?

If the other gears work, and the vehicle moves forward under its own power, then the problem is with the shift linkage or the transmission itself.

All the forward gears work fine & there was no indication of a problem prior to loosing reverse.The linkage seems fine from what I can tell. Could there be something internal with the linkage?