Why is my MCP server not connecting?

The most common causes are: incorrect executable path, missing environment variables, wrong transport type, or Node/Python not found in PATH. Check the client logs first.

How do I check MCP server logs in Claude Desktop?

On macOS, check ~/Library/Logs/Claude/. Look for mcp-server-*.log files. These contain the server startup output and any errors.

Does restarting fix MCP connection issues?

Often yes. Config changes only take effect after a full application restart, not a reload or refresh.

How to Fix "MCP Server Not Connecting" in an MCP Server

Quick Answer

MCP Server Not Connecting is most commonly caused by incorrect endpoint or command path. Check the steps below in order to isolate and fix the issue.

Affected Clients and Transports

Claude Desktop Cursor VS Code stdio streamable-http

Common Causes

Incorrect endpoint or command path
Missing credentials
Transport mismatch

Step-by-Step Diagnosis

Check the client logs. Open the client dev tools or log file and look for startup errors or JSON parse failures.
Verify the server starts manually. Run the server command in a terminal and confirm it prints no errors before waiting for input.
Use MCP Inspector. Run npx @modelcontextprotocol/inspector and connect to the server to inspect capabilities.
Validate credentials. Check that every required environment variable is set and has a valid value.
Restart the client. Config changes only take effect after a full client restart — not just a reload.

Resolution Checklist

Config file syntax is valid JSON/JSONC

Executable path or npx package name is correct

All required environment variables are set

Credentials have the required permissions/scopes

Client has been fully restarted

Server process has no port conflicts

MCPServer.in Editorial

Editorial Team

Published: 2026-08-05

Updated: 2026-08-05

Affected Clients and Transports

Common Causes

Step-by-Step Diagnosis

Resolution Checklist

Frequently Asked Questions