It also might be (as it proved in my case) that your address block (including the whole neighborhood from an ISP perspective) includes a compromised device. I discovered one of my neighbors has a compromised device that's sending a couple million spam emails per month, and it tainted the reputation of the entire network address block.

Well it happens on both my laptop and my phone, both of which are firefox with a lot of the fingerprinting stuff like useragent knocked out, as well as adblock, etc.