"oil-processing" unlocks "Petroluem fuel (Recipe)" but no solid fuel from petroleum.
In Factoriopedia are two petroluem fuels.
1) "Petroluem fuel" from Factorio+ (no base mod) without any a way to make it besides "alternative recipes" (->2).
2) "Petroluem fuel (Recipe)" from "Base mod > Factorio+" and makeable in chemical plant.
But no solid fuel from petroluem. Only from light and heavy oil.
In the file resources.lua from your mod is a recipe "solid-fuel-from-petroleum-gas" that makes "petroleum-fuel" from "petroleum-gas".
Should this recipe be named "petroleum-fuel-from-petroleum-gas" or similar?
If i'm not wrong the base recipe for solid fuel from petroleum is named "solid-fuel-from-petroleum-gas" and your resources.lua overrides it.