Hello, @yukiwakiyama417
I’m happy to hear that you finished your work with our plugin.
First of all, allow me to note that you can find all logs in the Stripe Marketplace Express plugin in your Stripe Dashboard.
It will help you to fix your issues easier.
We assume that this issue is related to the “Amount element”. The amount should be indicated in cents, and obligatory without decimals ( it means if you have $1 for a refund, then you have to put 100 cents).
Please check it in your settings and let me know if this helped.
Best regards,