My downstairs toilet iis overflowing. I had a plumber come out and the problem was not evident so he removed the toilet ran an auger through the line replaced the wax seal then left. When I ran my washing machine and it started to drain my toilet backed up and overflowed even after having turned off the water supply to the toilet.

Call the plumber back. He didn't get the clog. This time have him cycle the washer until it fills the line and then shut the washer down. Have him send his snake on down the line now. When the water rushes out with a "whoosh" he'll know he pumched through the blockage. Good luck, Tom