Is it the older type then? goodluck.
I would not pressure wash the new stuff; which the makers say soapy water wash mop and bucket only. Remove the moss with a scraper and brush and a few buckets should do it. Anychems is abig no no as they dont break down , get stuck in the crevices and then the sun hardens the rubber.
Find out if there is a landscape service looking after any gardens in the area and have a word; they will be trailering in water for plant purposes at the moment.