I believe they are a scam . I am writing a post about them . I also have this message after I won some coins and withdraw.
But this is a lie their website is perfectly working (try to connect from tor )
Both websites are working flawlessly on my phone and both PCs without using Tor or VPN. I'm from Romania if you're wondering.
I would not accuse PrimeDice of scamming right away. They have not only the best community I've ever seen on a gambling website but also fast support and I've never felt like their mechanism is rigged in any way. I'm one of the guys who quit their gambling addiction on a positive balance and with some beautiful profit.