Way for pay - error while creating (first time)

Good afternoon. This error indicates an incorrect merchant signature. Try to regenerate merchantSignature and insert a new one into the box settings

The matter is that if to make procedure once again. That is, after the error, click on "pay" again - then everything works fine. The error occurs only the first time when you click on pay. Can you see what the problem is. If you need a test order, we can create

Hello, please tell me what needs to be done to make it work correctly?
Works only the second time when you click "pay"

Maybe some modification needs to be done?
It gives an error for the first time, and if you press it again, it works correctly. How to fix it ?

Hello, please help me to solve this issue. The system works - it creates a link to pay but only in 2 cases
1. Immediately when the "Checkout" button is pressed
2. If already in the order click on "pay" - get an error - refresh the page and click on pay again. Then it only works, which is not very convenient. Maybe it needs some tweaking or something else?
Can we somehow link to generate payment? Type
/order number/amount to pay. It doesn't matter how it will be, the main thing is that a person in the personal account can click on pay - he was transferred to pay with a specified amount and that's it ... How to do it normally?