fgets() is not waiting for an input from the console

Question

I've written the following code for the ideal gas equation and been copying and pasting my input block from other areas of my code. When I get to debugging, the console isn't waiting for an input for the variable 'N'. When I placed an input before it accesses the vol function, it seemed to work but this isn't really what I want it to do. Any help with how to fix this?

#include <stdio.h>
#include <stdlib.h>
#define R 8.3145 //J/(mol.K)

double P; //Pressure in Pascals
double p; //Pressure in kilopascals
char str1[6];
char str2[6];
char str3[6];
double T; //Temperature in degrees Celsius
double TK; //Temperature in degrees Kelvin

double N; // moles in kmol
double n; // moles in mol
double V; // Volume in m3

void flusher(){
    //Function to flush the memory register
    fflush(stdout);
    fflush(stdin);
}

void Press(){
    //P is needed in Pa, needs to be converted from kPa
    //Obtaining pressure from user input and converting to the right magnitude of units
    printf("Please enter the partial pressure of the component (kPa): ");
    p = atof(fgets(str1,6,stdin));
    printf("You have entered %.3f kPa \n",p);

    //To use the Ideal Gas equation, pressure is needed in pascals
    P = 1000*p; //1000 Pa = 1 kPa
    printf("Therefore P = %f Pa \n\n",P);
    flusher();
}

void Temp(){
    /* T is in K, needs to be converted from deg C */
    printf("Please enter the system temperature (deg C): ");
    T = atof(fgets(str2,6,stdin));
    printf("You have entered %.3f deg C \n",T);
    TK = T + 273.15; //K
    printf("Therefore T = %f K \n\n",TK);
    flusher();
}

void vol(double Vm){
    // Calculates the occupied volume from the molar volume calculated through the Ideal Gas Law
    printf("Please enter the moles of component i (kmol): ");
    N = atof(fgets(str3,6,stdin));
    printf("\nYou have entered %f kmol\n",N);
    n = N*1000;
    V = Vm*n;
    printf("V = %f m3", V);
    flusher();
}

int main(){
    printf("R = %f \n",R);
    Press();
    Temp();

    // Calculating the volume of the component
    //PV = nRT tfr V_m = \frac{RT}{P}
    printf("P = %f Pa and T = %f K \n",P,TK);

    double Vm;
    Vm = (R*TK)/(P);
    printf("Molar volume = %f m3/mol \n\n",Vm);

    printf("Do you want to work out the occupied volume? [Y/N] ");
    char i = getchar();
    switch(i){
        case 'Y':
        case 'y':
        printf(" \n");
            vol(Vm);
        break;

        case 'N':
        case 'n':
            printf("You have picked No\n ");
        break;

        default:
        printf("Input not recognised\n");
    }
    flusher();
    return 0;
}