Fortbyte 92 is located South of the Volcano. Before you can collect the Fortbyte you must select the “Rock love”spray paint.
Once you have set the rock love spray paint you can go to the location. The Fortbyte is located on the small Island under the Volcano shown in this map:
Once you land in this location use your just set Rock Love spray paint near the Fortbyte and it is unlocked. Now you can collect it!
In this small video you can see the exact process and location to collect Fortbyte 92.