Presumably you used manually-logged time, or time which otherwise did NOT qualify for Upwork Payment Protection (such as time segments without adequate memos).
If that is what you did, then you made a mistake.
And the result is that if Upwork wasn't able to charge the client's credit card OR if the client intentionally disputed your time segments, you were not paid for that time.
We’re sorry to hear about this. On hourly contracts when a client fails to pay for the hours logged by the freelancer and those hours don’t meet the requirements for Hourly Protection, the payment may be reversed.
Our team will be reaching out to you via email with more information.