Here is a support document where you can start. Error: Services containing process crashed. ServiceName.GPServer instance has crashed and there is this solved thread: https://community.esri.com/thread/66569
Thanks! I checked PythonPath but the registry is pointing to the correct path C: \ Python27 \ ArcGISx6410.1 \ Lib; C: \ Python27 \ ArcGISx6410.1 \ DLLs; C: \ Python27 \ ArcGISx6410.1 \ Lib \ lib-tk.
I would have suggested to contact Esri support, but as of this year version 10.1 has been retired: https://support.esri.com/en/Products/Enterprise/arcgis-server/ArcGIS-Server/10-1#product-support and there is no support for this version. Do you have the possibility to upgrade to a more recent version?
You will have to provide a lot more details about the hardware server is installed on, how the service is configured (including scripts), etc in order for someone here to help.
Did you happen to have any Windows patches applied to your server machine lately?