How do I add an insurance payer for Electronic billing?

Hello there, 

I have a client who has Surest insurance which runs through United HealthCare. This is the new name for the United HealthCare policy that was once Bind. I have been advised by a representative to bill directly to Surest. I went in and had to manually add the insurance address, but it says "not supported" under claims filing enrollment. Can you tell me how to fix that and properly add this new insurance payer so that claims can be billed electronically? 

Thank you!