I set up vercel strorage, but continue to get this error: Error uploading file: Error: Only one file can be uploaded at a time.

Error uploading file: Error: Only one file can be uploaded at a time.
    at uploadFile (webpack-internal:///(api)/./pages/api/avatar/upload.js:23:19)
    at /path-tofile/frontend/node_modules/next/dist/compiled/next-server/pages-api.runtime.dev.js:21:3039
    at /path-tofile/frontend/node_modules/next/dist/server/lib/trace/tracer.js:133:36
    at NoopContextManager.with (/path-tofile/frontend/node_modules/next/dist/compiled/@opentelemetry/api/index.js:1:7062)
    at ContextAPI.with (/path-tofile/frontend/node_modules/next/dist/compiled/@opentelemetry/api/index.js:1:518)
    at NoopTracer.startActiveSpan (/path-tofile/frontend/node_modules/next/dist/compiled/@opentelemetry/api/index.js:1:18093)
    at ProxyTracer.startActiveSpan (/path-tofile/frontend/node_modules/next/dist/compiled/@opentelemetry/api/index.js:1:18854)
    at /path-tofile/frontend/node_modules/next/dist/server/lib/trace/tracer.js:122:103
    at NoopContextManager.with (/path-tofile/frontend/node_modules/next/dist/compiled/@opentelemetry/api/index.js:1:7062)
    at ContextAPI.with (/path-tofile/frontend/node_modules/next/dist/compiled/@opentelemetry/api/index.js:1:518)
    at NextTracerImpl.trace (/path-tofile/frontend/node_modules/next/dist/server/lib/trace/tracer.js:122:28)
    at K (/path-tofile/frontend/node_modules/next/dist/compiled/next-server/pages-api.runtime.dev.js:21:2970)
    at process.processTicksAndRejections (node:internal/process/task_queues:95:5)
    at async U.render (/path-tofile/frontend/node_modules/next/dist/compiled/next-server/pages-api.runtime.dev.js:21:3827)
    at async DevServer.runApi (/path-tofile/frontend/node_modules/next/dist/server/next-server.js:554:9)
 ⨯ Error: API route returned a Response object in the Node.js runtime, this is not supported. Please use `runtime: "edge"` instead: https://nextjs.org/docs/api-routes/edge-api-routes
    at K (/path-tofile/frontend/node_modules/next/dist/compiled/next-server/pages-api.runtime.dev.js:21:3093)
    at process.processTicksAndRejections (node:internal/process/task_queues:95:5)
    at async U.render (/path-tofile/frontend/node_modules/next/dist/compiled/next-server/pages-api.runtime.dev.js:21:3827)
    at async DevServer.runApi (/path-tofile/frontend/node_modules/next/dist/server/next-server.js:554:9)
    at async NextNodeServer.handleCatchallRenderRequest (/path-tofile/frontend/node_modules/next/dist/server/next-server.js:266:37)
    at async DevServer.handleRequestImpl (/path-tofile/frontend/node_modules/next/dist/server/base-server.js:791:17)
    at async /path-tofile/frontend/node_modules/next/dist/server/dev/next-dev-server.js:331:20
    at async Span.traceAsyncFn (/path-tofile/frontend/node_modules/next/dist/trace/trace.js:151:20)
    at async DevServer.handleRequest (/path-tofile/frontend/node_modules/next/dist/server/dev/next-dev-server.js:328:24)
    at async invokeRender (/path-tofile/frontend/node_modules/next/dist/server/lib/router-server.js:174:21)
    at async handleRequest (/path-tofile/frontend/node_modules/next/dist/server/lib/router-server.js:353:24)
    at async requestHandlerImpl (/path-tofile/frontend/node_modules/next/dist/server/lib/router-server.js:377:13)
    at async Server.requestListener (/path-tofile/frontend/node_modules/next/dist/server/lib/start-server.js:140:13) {
  page: '/api/avatar/upload'
}

Can you help me resolve this issue, thanks in advance.