Credit Score Management

I have brilliant credit and zero debt. My house is paid for, debt free, and I do not have any outstanding debt. I have had loans in the past, but I’ve paid them off. Therefore, I do not have a credit score. I want to tap into the equity on my house and take out a second mortgage on my home, but the bank says that I do not have a credit score. Does anyone have any thoughts on how I can get a competitive rate with no score?