If invisible players or mobs remain hard to spot while Visible Invisibility Shaders is installed, another video setting or pack is preventing the core-shader tweak from altering potion particles.
Resolving Pack Priority and Shader Conflicts
Core shaders use the vanilla resource pipeline and can be overridden by other visual tweaks.
1. Open Options > Resource Packs and move Visible Invisibility Shaders to the very top of the active column so texture or utility packs below it cannot replace its core-shader files or particle textures.
2. If you run a shader loader like OptiFine or Iris, open Options > Video Settings > Shader Packs and set external shaders to Off. Full graphical shader packs replace Minecraft's vanilla rendering pipeline and stop core-shader tricks from functioning.
Checking Particle Visibility Limits
Because the TrueSight effect alters invisibility particles rather than drawing solid player models, particles must actually spawn in the world to be highlighted.
1. Confirm Options > Video Settings > Particles is set to All, as lower settings reduce or completely hide potion swirls on your screen.
2. Keep in mind that if a custom server applies an invisibility effect with particles disabled on the server side, no particles are sent to your game—only targets actively emitting invisibility potion particles will display the TrueSight marker.