>>45170160Usually if you have this kind of bug the reason is a bad configuration.
Step 1, go to the grass you should encounter the Pokemon.
Step 2, press F9, it will show a UI telling all the Available Pokémon on which condition.
Step 3, check that you're walking on a tile that is assigned to the right combination of "System Tag" + "Terrain Tag".
Additional Step: Check that your RMXP Map is linked to the right Zone in Ruby Host.