Unable to run (installed) Hubstaff

I am using Kubuntu 18.04 and I want to use Hubstaff, which was successfully installed according to its interface, but in the terminal it showed terminate called after throwing an instance of 'std::runtime_error' what(): locale::facet::_S_create_c_locale name not valid . The same message appears when I go ./HubstaffClient.bin.x86_64. And here is the full message:

2019-03-22 14:25:18.017705 [DEBUG] [0x3918de0] ui_style_adwaita.cpp:437  DEfinineg adwaita 2019-03-22 14:25:18.018120 [DEBUG] [0x3918de0] fltk.cpp:218  Define scheme: adwaita 2019-03-22 14:25:18.018308 [DEBUG] [0x3918de0] fltk.cpp:230  Define scheme: adwaita first box: 64 2019-03-22 14:25:18.028276 [DEBUG] [0x3918de0] fltk.cpp:218  Define scheme: cairo 2019-03-22 14:25:18.028346 [DEBUG] [0x3918de0] fltk.cpp:230  Define scheme: cairo first box: 67 2019-03-22 14:25:18.028386 [DEBUG] [0x3918de0] fltk_cairo.cpp:565  cairo_box_start : 67 2019-03-22 14:25:18.028513 [DEBUG] [0x3918de0] Log.cpp:230  Echoing to stdout : 1 2019-03-22 14:25:18.028554 [DEBUG] [0x3918de0] main.cpp:20   Hubstaff client started terminate called after throwing an instance of 'std::runtime_error'    what():  locale::facet::_S_create_c_locale name not valid Aborted (core dumped)` 

Thank you.