Access can be restricted at the platform level for security reasons: specific IP addresses, entire countries, or known malicious sources may be blocked to protect the service and its users from abuse. If you believe you were blocked in error, please contact support so it can be reviewed.
This is separate from the geo-targeting a link owner can set up themselves (see the earlier FAQ on location-based redirects), which controls where visitors are sent, not whether they can access the service at all.