WP Simple Pay automatically limits the number of consecutive requests that a single IP address can make.
By default, WP Simple Pay limits requests to 1.5-hour timeframes, meaning once the limit is reached, the user must wait 1.5 hours before the request will be completed.
Standard usage of WP Simple Pay will very rarely cause users to reach this rate limit, however as a site administrator you might encounter it while testing your payment forms.
Clear Rate Limit Log
If you need to clear all existing IPs that have been tracked for rate limiting, you can delete the .log file located in/wp-content/uploads/abc-123-wpsp-rate-limiting.log The filename will contain a unique hash rather than abc-123-wpsp-rate-limiting.
Increase the Number of Allowed Requests
If you need to increase or decrease this limit, you can add the following custom code snippet to your website: Add More Aggressive Rate Limiting.