I've made mucho money selling Bio-clean over the years. I also believe in this product, but only after the line is brought back to as new condition as it can. Jet rodding will do this.
Bio-clean is a preventive maintenance product, not a drano clearing every thing including dried concrete product that you see advertised on TV.

This line has a history of blockages. Think about what is being said here. Probably some settling over the years, a few bellies, not yours or mine but the drain line. An enzyme product is outstanding for this application. This is my humble opinion and what my billfold tells me!