Car Park API Rate Limiting

I was able to make a single request to /carpark using postman with my API key. It worked first time and I got back the list of parks.

The second, and every request since then has returned ‘Message’: ‘Your API quota or rate limit has been exceeded. If you think you need a increased quota or rate limit’

Yet, if I use my key in the “Explore API” page, it works consistently. Same issue using curl or python requests.

curl request is curl --header "Authorization: apikey xxxxxx"

Any suggestion what I am doing wrong?