Reassembling main.dart$main-2708069695012231 failed: [Sentinel kind: Collected, valueAsString: ] from ext.flutter.reassemble() #0 new _OutstandingRequest (package:vm_service/src/vm_service.dart:1930:45) #1 VmService._call (package:vm_service/src/vm_service.dart:2499:21) #2 VmService.callServiceExtension (package:vm_service/src/vm_service.dart:2470:14) #3 FlutterVmService._checkedCallServiceExtension (package:flutter_tools/src/vmservice.dart:868:28) #4 FlutterVmService.invokeFlutterExtensionRpcRaw (package:flutter_tools/src/vmservice.dart:887:49) #5 FlutterVmService.flutterReassemble (package:flutter_tools/src/vmservice.dart:728:12) #6 _defaultReassembleHelper (package:flutter_tools/src/run_hot.dart:1337:63) #7 HotRunner._reloadSources (package:flutter_tools/src/run_hot.dart:983:47) #8 HotRunner._hotReloadHelper (package:flutter_tools/src/run_hot.dart:868:16) #9 HotRunner.restart (package:flutter_tools/src/run_hot.dart:765:36) #10 _AsyncCompleter.complete (dart:async/future_impl.dart:41:3) #11 DebounceOperationQueue.queueAndDebounce.. (package:flutter_tools/src/commands/daemon.dart:1695:27)  

Fix

Your Flutter app is frozen. Just shut down your app and reinstall.