If your framework does not utilize server-side rendering:
Run npm i @google/model-viewer and add import '@google/model-viewer' to any files that utilize <Echo/>
If your framework does utilize server-side rendering:
Issues arise when components or pages importing model-viewer are rendered server-side. To most reliably resolve this issue for SSR apps, provide model-viewer via a script element in your _document file eg: <script type="module" src="https://unpkg.com/@google/model-viewer/dist/model-viewer.min.js"></script>
For TypeScript apps:
If you do not have a globals.d.ts file, create one within your app src folder, add the line declare module 'echo3d'; and save the file to resolve compiler typing errors.