VAPI with Zapier MCP returns 500 error as Session ...
# supportj
Josh
05/08/2025, 11:07 PMHello,
I've been trying to get Zapiar MCP working with VAPI to do some integration work but I've been consistently getting an error when testing the tool.
I thought maybe the issue was specific to testing but when trying a tool in a call it's also not working.
I originally was using Zapier MCP but also tried Zapier Actions MCP. Both of which are non-functional.
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{
"error": "Failed to connect to MCP server: Error POSTing to endpoint (HTTP 400): {\"jsonrpc\":\"2.0\",\"error\":{\"code\":-32603,\"message\":\"Internal error: Session not found\"},\"id\":null}"
}v
Vapi Support Bot
05/08/2025, 11:07 PMThanks for sharing the detailed error message and your experience with both Zapier MCP and Zapier Actions MCP. I understand how frustrating it can be to encounter a "Session not found" error, especially after trying multiple approaches. While I don't have specific information on this error or its resolution, your description and the error details you've provided are clear and thorough, which should be helpful for further investigation. If you have any additional context about your setup or steps taken, feel free to share, and I'll do my best to assist further.
Vapi Support Bot
05/08/2025, 11:07 PMThanks for sharing the detailed error message and your experience with both Zapier MCP and Zapier Actions MCP. I understand how frustrating it can be to encounter a "Session not found" error, especially after trying multiple approaches. While I don't have specific information on this error or its resolution, your description and the error details you've provided are clear and thorough, which should be helpful for further investigation. If you have any additional context about your setup or steps taken, feel free to share, and I'll do my best to assist further.
Vapi Support Bot
05/08/2025, 11:07 PMThanks for sharing the detailed error message and context about your experience with integrating VAPI and Zapier MCP. I see you've tried both Zapier MCP and Zapier Actions MCP and are encountering a "Session not found" error with a 400 status, along with a 500 error on the request. I understand how frustrating it can be to run into these kinds of issues during integration work.
Vapi Support Bot
05/08/2025, 11:07 PMThanks for sharing the detailed error message and context about your experience with integrating VAPI and Zapier MCP. I see you've tried both Zapier MCP and Zapier Actions MCP and are encountering a "Session not found" error with a 400 status, along with a 500 error on the request. I understand how frustrating it can be to run into these kinds of issues during integration work.
k
Kings_big💫
05/09/2025, 8:23 AMThe 500 error means Zapier’s MCP server is failing, double-check your MCP URL, ensure the Zap is published and active, test with Postman, and contact Zapier support if the issue persists thanks
m
max
05/09/2025, 4:54 PM@Kings_big💫 I have the same issue with both Zapier and n8n from one day to the next. All are published and they work with other systems. Still nothing works with VAPI.
i
isaac
05/10/2025, 4:41 PMI am experiencing the same bug, I can connect to my mcp server from vs code, but not vapi
k
Kings_big💫
05/10/2025, 4:47 PMWe are doing some logs migration, so please wait for some time.
j
Josh
05/11/2025, 12:57 AMThis appears to be resolved on the Daily channel.