I am a new ChipMixer user. I spent 3-4 days testing with trivial amounts of BTC. When I was satisfied that the service worked exactly as documented, I started to move much larger amount of BTC through. I also made a donation for the use of the service.
If this is just DDOS downtime... that is some bad luck on my part.
I have no official information to give you guys, but it most probably is a little bit of bad luck, indeed. There were ChipMixer downtimes before and they will most likely happen again - probably partly for scheduled maintenance, but also simply due to the challenges that come with running such an anonymous website, offering such anonymous services (attacks, hacking attempts, ...).