When I send payment to a testnet address generated by Mycelium Gear, it doesn't see the transaction even when it's included in a block.
Blockcypher.com, blockexplorer.com, blockchain.info and blocktrail.com see the transaction, though
blocktrail seems to have indexing lag: it can't find the transaction by payment address, only by transaction id.
If Gear uses blocktrail API, this could be the reason.
Does anyone know a workaround, without using block chain exploration apis by myself?