Compilation error: expected nested-name-specifier

[chriskuku]

I'm trying to build Esp32_oscilloscope.ino using Arduino-IDE 2.3.2 and I'm getting somthing like this: (output has scrolled out of the output window, so I cannot see where the error initially occurs.

 |             ^~~~~~~~
/Users/kuku/Esp32_oscilloscope/fsString.h:46:13: note:   candidate expects 1 argument, 2 provided
/Users/kuku/Esp32_oscilloscope/fsString.h:44:13: note: candidate: 'fsString<N>::fsString() [with unsigned int N = 300]'
   44 |             fsString () {}                                      // for declarations like fsString<15> a;
      |             ^~~~~~~~
/Users/kuku/Esp32_oscilloscope/fsString.h:44:13: note:   candidate expects 0 arguments, 2 provided

exit status 1

Compilation error: expected nested-name-specifier