Interpreter not outputting characters

#include <iostream>
#include <algorithm>
#include <vector>

using namespace std;

int main()
{
    vector<int> tape(30000, 0); // tape with 30000 cells
    int ptr = 0;                // pointer to the current cell (memory address)
    int code_ptr = 0;           // pointer to current code instruction
    
    string code;
    getline(cin, code);

    while (code_ptr < code.size())
    {
        char instruction = code[code_ptr];

        // instructions
        // https://en.wikipedia.org/wiki/[redacted]Language_design
        switch (instruction)
        {
        case '>':   // increment cell pointer
            ++ptr;
            break;

        case '<':   // decrement cell pointer
            --ptr;
            break;

        case '+':   // increment byte at ptr cell
            ++tape[ptr];
            break;

        case '-':   // decrement byte at ptr cell
            --tape[ptr];
            break;

        case '.':   // print byte at ptr cell
            cout << (char)tape[ptr];
            break;

        case ',':   // accept one byte of input, store it's value at ptr cell
            tape[ptr] = cin.get();
            break;

        case '[':   // start a loop
            if (tape[ptr] == 0)
            {
                int loop_count = 1;
                while (loop_count > 0)
                {
                    ++code_ptr;
                    if (code[code_ptr] == '[')
                        ++loop_count;
                    else if (code[code_ptr] == ']')
                        --loop_count;
                }
            }
            break;

        case ']':   // end a loop
            if (code[code_ptr] != 0)
            {
                int loop_count = 1;
                while (loop_count > 0)
                {
                    --code_ptr;
                    if (code[code_ptr] == '[')
                        --loop_count;
                    else if (code[code_ptr] == ']')
                        ++loop_count;
                }
            }
            break;
        
        default:
            cout << "\nUnrecognized character: " << code[code_ptr];
            break;
        }

        ++code_ptr;
    }

    return 0;
}

>++++++++[<+++++++++>-]<.