Shopify added a new feature called "Request Fulfillment" for the orders.
While it may useful in few cases, it creates some orders errors and make you unable to place the orders on Topdser.
To avoid this issue, please DO NOT CLICK "Request Fulfillment" on your order on Shopify.
How to fix it
In case you have accidentally clicked on "Request Fulfillment" on a new order on Shopify.
You will see the status as "In Progress"in Shopify.
And order is unable to fulfill on Topdser.
To recover the order status to unfulfilled, you must fulfill the order on Shopify first and then cancel fulfillment.
First, Click "More" and select "Mark as fulfilled".
The order will become fulfilled on Shopify.
Then click on the "More" button and select "Cancel Fulfillment".
The order will become unfulfilled on Shopify again, now you can go to Topdser and place the order normally.