Unrecognized packages often mean they aren’t installed correctly or are missing from `node_modules`. Running `npm install` again usually resolves this.

If your Node.js application fails to recognize installed npm packages, it’s likely due to issues with the node_modules folder, an incomplete or corrupt installation, or an incorrect configuration. First, verify that the package is listed in your package.json under dependencies or devDependencies. If the package is present, delete the node_modules folder and the package-lock.json file, then run npm install to reinstall all dependencies fresh, as corrupted files in node_modules can often cause unrecognized packages. In some cases, conflicting versions of a package may be globally installed or installed within subdirectories, leading to confusion for Node.js when importing modules. Running npm ls <package-name> can reveal if multiple versions of a package are installed. Another troubleshooting step is to check for the presence of .npmrc files or custom NODE_PATH configurations, which might be altering the lookup paths for modules. If using a monorepo or workspaces, ensure each package or workspace is correctly referenced. In some instances, using npx to run commands ensures the app pulls the correct package version without relying on a global or previously cached version, helping to resolve conflicts.