Jupyter - failed to start the kernel

i am suddenly getting the following error when trying to launch a jupyter-notebook: "Failed to start the kernel"- Unhandled error. Any ideas how to fix this?

Traceback (most recent call last):  File "C:\Users\USER\AppData\Local\Continuum\anaconda3\lib\site-packages\tornado\web.py", line 1699, in _execute    result = await result  File "C:\Users\USER\AppData\Local\Continuum\anaconda3\lib\site-packages\tornado\gen.py", line 742, in run    yielded = self.gen.throw(*exc_info)  # type: ignore  File "C:\Users\USER\AppData\Local\Continuum\anaconda3\lib\site-packages\notebook\services\sessions\handlers.py", line 72, in post    type=mtype))  File "C:\Users\USER\AppData\Local\Continuum\anaconda3\lib\site-packages\tornado\gen.py", line 735, in run    value = future.result()  File "C:\Users\USER\AppData\Local\Continuum\anaconda3\lib\site-packages\tornado\gen.py", line 742, in run    yielded = self.gen.throw(*exc_info)  # type: ignore  File "C:\Users\USER\AppData\Local\Continuum\anaconda3\lib\site-packages\notebook\services\sessions\sessionmanager.py", line 88, in create_session    kernel_id = yield self.start_kernel_for_session(session_id, path, name, type, kernel_name)  File "C:\Users\USER\AppData\Local\Continuum\anaconda3\lib\site-packages\tornado\gen.py", line 735, in run    value = future.result()  File "C:\Users\USER\AppData\Local\Continuum\anaconda3\lib\site-packages\tornado\gen.py", line 742, in run    yielded = self.gen.throw(*exc_info)  # type: ignore  File "C:\Users\USER\AppData\Local\Continuum\anaconda3\lib\site-packages\notebook\services\sessions\sessionmanager.py", line 101, in start_kernel_for_session    self.kernel_manager.start_kernel(path=kernel_path, kernel_name=kernel_name)  File "C:\Users\USER\AppData\Local\Continuum\anaconda3\lib\site-packages\tornado\gen.py", line 735, in run    value = future.result()  File "C:\Users\USER\AppData\Local\Continuum\anaconda3\lib\site-packages\tornado\gen.py", line 209, in wrapper    yielded = next(result)  File "C:\Users\USER\AppData\Local\Continuum\anaconda3\lib\site-packages\notebook\services\kernels\kernelmanager.py", line 168, in start_kernel    super(MappingKernelManager, self).start_kernel(**kwargs)  File "C:\Users\USER\AppData\Local\Continuum\anaconda3\lib\site-packages\jupyter_client\multikernelmanager.py", line 110, in start_kernel    km.start_kernel(**kwargs)  File "C:\Users\USER\AppData\Local\Continuum\anaconda3\lib\site-packages\jupyter_client\manager.py", line 259, in start_kernel    **kw)  File "C:\Users\USER\AppData\Local\Continuum\anaconda3\lib\site-packages\jupyter_client\manager.py", line 204, in _launch_kernel    return launch_kernel(kernel_cmd, **kw)  File "C:\Users\USER\AppData\Local\Continuum\anaconda3\lib\site-packages\jupyter_client\launcher.py", line 138, in launch_kernel    proc = Popen(cmd, **kwargs)  File "C:\Users\USER\AppData\Local\Continuum\anaconda3\lib\subprocess.py", line 775, in __init__    restore_signals, start_new_session)  File "C:\Users\USER\AppData\Local\Continuum\anaconda3\lib\subprocess.py", line 1178, in _execute_child    startupinfo)FileNotFoundError: [WinError 2] Das System kann die angegebene Datei nicht finden