On line nine in the SDHI_2.5_AvionicsRing's .cfg, it has:
"model = SDHI/Service Module System/Parts/SDHI_2.5_ServiceModule/AvionicsRing"

when it should be
"model = SDHI/Service Module System/Parts/SDHI_2.5_AvionicsRing"
as per the the way you have everything pathed in the V1.9 release.

EDIT: Still not seeing the Avionics Ring.

Oops, I forgot to mention that I've consolidated the folder structure slightly, by moving the Avionics Ring model to the same folder as the Service Module, to eliminate duplicate textures.

After consolidating the two folders to how it is presented in GitHub, the avionic ring appeared in the VAB and in game.