This question already has an answer here:
So I tried to transfer funds from shapeshifter to monero gui wallet. The shapeshift website that the transaction was completed. But the funds never showed up. I asked the support of ShapeShifter to reverse the transaction (which they did immediately). My wallet is fully synced, so i'm wondering if I made a mistake without how I inputted my wallet information.
What I did was that i put down my monero gui wallet address and I generated a new payment ID. I notice now that I can specify the amount that i expect to receive. Do i need to fill that out when I generate a payment ID? Or is there something else that is going wrong with my GUI wallet