After trying several potential options to solve this I may have found a possible explanation (but not 100%).
I've saved my poles as shading selected objects and started a fresh new simulation with a random meteorological file to avoid any external effect of my 3D : no effect, still not snapping.
I've opened the shading selected objects in PVsyst 7.4.8 and again started a fresh new simulation : no effect, still not snapping.
Then I've noticed that the snapping was working for several poles at the same altitude so I've tried changing the altitude of my other poles and then it worked with no issue. It means that depending of the altitude (I don't know what the tolerance is), the snapping function is not able to find the edge to connect the end of the cable object.
1st picture, they are more or less at the same Z coordinates ; snapping is working perfectly
2nd picture, the poles are at a different altitude, not snapping, mainly X coordinates which is affected by the poles location
Now what I can't explain is that the snapping is working for another pole at a different altitude, mainly with a Y coordinates affected by the poles location...
I can share a *.SHO file with my poles position and cables snapping/not snapping to help identify the issue, if necessary.
Thanks for your feedback,
D