Likely stale shares which you can check in your logs and history. Quickest resolution seems to be emailing support. Good luck:
Are there payouts for stale shares?
A valid share is contributed before the winning block. In turn, a stale share is a share that was sent after a block was already solved.
Payment for stale shares is made - it is 50%.
For up to 5% of stale shares, the conditions are the same. Starting from 5% and above, the pool freezes the payouts, meaning you won’t get paid for your stale shares. If the problem of high stales persists for 24 hours, the wallet is blacklisted and payouts are frozen until further notice.
Such radical measures are related to the fact that fraudulent miners abuse our stale shares payout system. Thank you for understanding and thank you for using our ecosystem.