callin.io cloud MCP server issues

Hi,

I'm encountering issues with the callin.io cloud-based MCP server.

The Cloudflare Playground ( https://playground.ai.cloudflare.com ) is reporting:
Failed to connect via SSE: SSE error: Load failed.

When attempting to link a Retell AI Agent to callin.io, it remains stuck in a "Loading..." state while trying to select tools:

image1118×366 17.5 KB

Has anyone else experienced this issue, or do you have a potential solution?

Thanks

Jörg