network for good

I’m enrolling my nonprofit in Walmart Spark Good Round Up. Walmart says my organization is eligible and directs me to Network for Good to set up electronic payments. When I enter my EIN to register, Network for Good says the EIN is incorrect or not found in the database. I have my IRS 501(c)(3) determination letter. I need help getting my organization recognized so I can complete my Walmart Spark Good Round Up payment setup.”