Neighbors sewer pipe going through my lot

[Thripura Vemireddy]

Hi

I bought a lot in a subdivision and got Permit for building a new home. When we started digging for basement we discovered that neighbors sewer line going from my lot(where my house envelop is) and Connected to my sewer tap. 

The neighbor house has a sewer tap, but they did not connect to it.

I called to County sewer department, health department, no one is coming forward to help.

The contractor who built the neighbors house did it unauthorized, the buyer is unware. The house is sold in Feb 2021.

Is the seller of the house liable to fix the issue? as it is within one year of sale.

Anyone had this kind of situation and how it got resolved.

I am incurring financial loss as my work is stopped.

what are my options now.

Appreciate your suggestions.

Thank you 

Reddy