linking url from InitTxn has error

[StrongMan988]

Hello,Bro. I'm very happy to see your great project. Recently, I'm establishing a tool for full body tracking. And I want to implement a function that my users can go shopping in my application.However,I tried to get responses from steamwork web api which is 'https://partner.steam-api.com/ISteamMicroTxnSandBox/InitTxn/v3/'. I could enture that I get the true responses which include a url. But when I linked this url, It is always failed to load, and display a information that is 'Sorry for the transaction authorization error, please try again'. How can I solve it ? If you could help me ,I would be very very very grateful !!!