API access blocked from IP address

It looks like one of our IP addresses has been blocked from accessing the REST API.

Any request to the API from the blocked IP address returns a generic “403 Forbidden” response:

<head><title>403 Forbidden</title></head>
<center><h1>403 Forbidden</h1></center>

It doesn’t appear to be the API credentials as they continue to work when used from other IP addresses.

Is it possible to get an IP address unblocked from the API?