I've fiddled a bit with Wireshark and had a look at the full response you receive from Amazon. (See below, I only removed the unique identifiers as to not cause more problems when that API Key was reused by a Spambot or so)
AWS Access Key ID: AKIAJ*********HTA. You are submitting requests too quickly. Please retry your requests at a slower rate.
What you can get from this message is the following: Apparently Amazon has set new limits on using this Merchant API and Spacial is exceeding them by far. This could be either due to Amazon phasing out this API (thus reducing the number of requests deemed OK) or due to the API not being meant for multi-tenant applications like SAM Broadcaster where people from around the world will all use Spacial's API Key to call the Amazon API at a high rate and at all times of the day.
This could also be a problem with Spacial's Associate ID being revoked access completely due to not generating any revenue at all.
See this document for more insight on how the number/rate of requests is calculated based on revenue generated from the Amazon Associate ID used in the Product Search API: https://docs.aws.amazon.com/AWSECommerc ... guidelines