Hi ,
I'm using this endpoint with success
https://api.meraki.com/api/v1/organizations/xxxxx/auth/radius/servers
[{"serverId":"xxxx","name":"xxxx","address":"xx","modes":[{"mode":"auth","port":1812},{"mode":"accounting","port":1813}]},{"serverId":"xxxx","name":"xxxx","address":"xxxx","modes":[{"mode":"auth","port":1812},{"mode":"accounting","port":1813}]},{"serverId":"xxxx","name":"xxxx","address":"xxxx","modes":[{"mode":"auth","port":1812},{"mode":"accounting","port":1813}]},{"serverId":"xxxx","name":"xxxx","address":"xxxx","modes":[{"mode":"auth","port":1812},{"mode":"accounting","port":1813}]}]
Can you paste the complete URL that you are using ?