Please check and confirm if you correctly included the Memo (or Destination Tag) when you initiated the transaction.
XRP deposits to MAX require a specific Memo to identify which user's account to credit. If the Memo was missing or incorrect, the funds cannot be credited to your account automatically.
If this has happened, please email our customer support at max@maicoin.com and provide your Transaction ID (TXID). A member of our team will then assist you.