Good day @RimsChoice,
Thank you for posting to the PayPal community.
BAD_INPUT_ERROR, this is an issue with merchant internal website which is passing invalid payment API requests to PayPal system.
To resolve the issue, merchant should contact their website developer or the support of your third party platform(eCommerce) to cross check their website integration and pass the valid payment API requests to PayPal system.
Sample HTML button code : View sample HTML code that shows various payment features and options for each PayPal payment button.
Use the following samples as a starting point to create your own HTML payment button code:
If your still facing issue, please create a MTS ticket via - https://www.paypal-support.com/s/?language=en_US with the detail information and error details.
If this post or any other was helpful, please enrich the community by giving kudos or accepting it as a solution.