In case 1 I entered numofitems but in case 2 it disappeared? Give me an explanation and how to fix it?

int main(){
    
    int opt,n;
    struct orders ord;
    struct orders order;
    char saveBill = 'y',contFlag = 'y';
    char name[50];
    FILE *fp;
       //dashboard
    while(contFlag == 'y'){
    system("clear");
    float total = 0;
    int invoiceFound = 0;
    printf("\t============ADV. RESTAURANT============");
    printf("\n\nPlease select your prefered operation");
    printf("\n\n1.Generate Invoice");
    printf("\n2.Show all Invoices");
    printf("\n3.Search Invoice");
    printf("\n4.Exit");

    printf("\n\nYour choice:\t");
    scanf("%d",&opt);
    fgetc(stdin);
    switch(opt){
        case 1:
        system("clear");
        printf("\nPlease enter the name of the customer:\t");
        fgets(ord.customer,50,stdin);
        ord.customer[strlen(ord.customer)-1] = 0;
        strcpy(ord.date,__DATE__);
        printf("\nPlease enter the number of items:\t");
        scanf("%d",&n);
        ord.numOfItems = n;
        for(int i=0;i<n;i++){
            fgetc(stdin);
            printf("\n\n");
            printf("Please enter the item %d:\t",i+1);
            fgets(ord.itm[i].item,20,stdin);
            ord.itm[i].item[strlen(ord.itm[i].item)-1]=0;
            printf("Please enter the quantity:\t");
            scanf("%d",&ord.itm[i].qty);
            printf("Please enter the unit price:\t");
            scanf("%f",&ord.itm[i].price);
            total += ord.itm[i].qty * ord.itm[i].price;
        }

        generateBillHeader(ord.customer,ord.date);
        for(int i=0;i<ord.numOfItems;i++){
            generateBillBody(ord.itm[i].item,ord.itm[i].qty,ord.itm[i].price);
        }
        generateBillFooter(total);

        printf("\nDo you want to save the invoice [y/n]:\t");
        scanf("%s",&saveBill);

        if(saveBill == 'y'){
            fp = fopen("RestaurantBill.dat","a+");
            fwrite(&ord,sizeof(struct orders),1,fp);
            if(fwrite != 0)
            printf("\nSuccessfully saved");
            else 
            printf("\nError saving");
            fclose(fp);
        }
        break;

        case 2:
        system("clear");
        fp = fopen("RestaurantBill.dat","r");
        printf("\n  *****Your Previous Invoices*****\n");
        while(fread(&order,sizeof(struct orders),1,fp)){
            float tot = 0;
            generateBillHeader(order.customer,order.date);
            for(int i=0;i<order.numOfItems;i++){
                generateBillBody(order.itm[i].item,order.itm[i].qty,order.itm[i].price);
                tot+=order.itm[i].qty * order.itm[i].price;
            }
            generateBillFooter(tot);
        }
        fclose(fp);
        break;

when i re-enter that variable in case 2 it works but it doesn't work when i export file with different data