Do you use a microwallet username instead of a bitcoin address?
If so did you get over the 3500 Satoshi minimum?

Or if you used a BTC address instead did you see this note on their page?
"Payments are sent via Microwallet.org.Your withdrawn funds if lower than 5800 Satoshi are stored there and released to your BTC address when equal to or greater than 5800 Satoshi to minimize fees!"

Thanks for the report.