Like population, influence slowly increases over time. However, it is localized to a single region, and will go down in regions you aren't in. It also increases faster if you have a lot of WA endorsements.
INTP, -4.25 Economic Left/Right, -4.1 Social Libertarian/Authoritarian, tastes like chicken.
I do use NS stats, thank you very much. Funny Quotes
The reason it is zero is likely because you just got into a region, therefor you have no influence yet. After you're in there for the next major update the game will assign you some. Joining the WA and getting endorsements really sky rockets it as stated by the person before me.