I can also confirm that I cannot access their clearnet site but their Tor site is working normally. They appear to be dealing with a number of other users who are having the same issue as you, where they have made a deposit which has not been credited:
I just sent over 1200 euros to Cryptomixer.io, to the correct address. The transaction is confirmed but no coins are received
I've completed my transfer site is I won't be back. I've used it a lot since a long time ago, what's up? I also sent you an email. Please reply.
The clearnet website is temporarily down. Kindly, use the chat with support on our tor-mirror
cryptomixns23scr.onion or PM me directly the transaction details. Ill follow your issue.
It is very unlikely this is a scam attempt. Simply PM their account above and wait for their resolution.