Can´t get backto oreo

Hello. I was given this phone as a gift. It has the Pie beta installed and I would like to get it back to Oreo. But after I downloaded the rollback ROM, when I try to install it I get the same message as on the other posts. What can I do to get it back to Oreo?

So, no chance of help on getting back to oreo?

Hi f.salazar.ramos.personal,

Could you show us your error message?
Please check your PM for a message I have sent you.

Thank you