I sent over a small amount as a test on Cryptomixer.io - I did not receive one of the transactions. I e-mailed support and they asked for the letter of guarantee. Sent it to them but no further response after that
Could you kindly check the real e-mail originator? You can find here
how-to article. I can suppose that you had become a victim of a phishing-website. Our support do not have an opened issues that matches your case description. In alternative you can PM me with your Letter of Guarantee or send it to this email:
support@cryptomixer.io. Ill follow your issue.