Shaders no longer shows in screen

I encountered quite a frustrating problem yesterday while exploring shaders, i used to play on paraLLEl n64 core with 4x internal resolution and a bilinear shader to fix pixelated HUD in games that resolution upscale gives, i wanted to explore a little more the shaders but for some reasons when i changed to another shader they just randomly stopped to display on screen, like no shaders at all are applied after restarting even while retroarch crearly says that the shader has been loaded I tried to uninstall and reinstall retroarch but even with that shaders like 4xsal-level2-hq.slangp or the simple bilinear.slangp ones still not shows up anymore Any idea of what could have happened here ?