Have you added it to 00_modifier_definitions?
There are instructions in 00_religions.txt:
"# Religion-specific opinion can be added to modifiers (E.G., norse_pagan_opinion = 5), but the modifier *has* to be defined in 00_modifier_definitions.txt as well. It also needs localisation. Works for groups as well"
There are instructions in 00_religions.txt:
"# Religion-specific opinion can be added to modifiers (E.G., norse_pagan_opinion = 5), but the modifier *has* to be defined in 00_modifier_definitions.txt as well. It also needs localisation. Works for groups as well"