How can I fix this code

To add to what Richard has said, you would have spotted the problem yourself in minutes if you had used the debugger to look at your code while it's running.
Debuggers are a tool that lets you add breakpoints, step through your code line by line, and look at the current value of variables to help you understand why code doesn't do exactly what you expect, and you should get used to using one because compiling does not mean your code is right! :laugh:

Think of the development process as writing an email: compiling successfully means that you wrote the email in the right language - English, rather than German for example - not that the email contained the message you wanted to send.

So now you enter the second stage of development (in reality it's the fourth or fifth, but you'll come to the earlier stages later): Testing and Debugging.

Start by looking at what it does do, and how that differs from what you wanted. This is important, because it give you information as to why it's doing it. For example, if a program is intended to let the user enter a number and it doubles it and prints the answer, then if the input / output was like this:

Input   Expected output    Actual output
  1            2                 1
  2            4                 4
  3            6                 9
  4            8                16

Then it's fairly obvious that the problem is with the bit which doubles it - it's not adding itself to itself, or multiplying it by 2, it's multiplying it by itself and returning the square of the input.
So with that, you can look at the code and it's obvious that it's somewhere here:

private int Double(int value)
   {
   return value * value;
   }

Once you have an idea what might be going wrong, start using the debugger to find out why. Put a breakpoint on the first line of the method, and run your app. When it reaches the breakpoint, the debugger will stop, and hand control over to you. You can now run your code line-by-line (called "single stepping") and look at (or even change) variable contents as necessary (heck, you can even change the code and try again if you need to).
Think about what each line in the code should do before you execute it, and compare that to what it actually did when you use the "Step over" button to execute each line in turn. Did it do what you expect? If so, move on to the next line.
If not, why not? How does it differ?
Hopefully, that should help you locate which part of that code has a problem, and what the problem is.
This is a skill, and it's one which is well worth developing as it helps you in the real world as well as in development. And like all skills, it only improves by use!

How you use it depends on your compiler system, but a quick Google for the name of your IDE and "debugger" should give you the info you need.
And learning to use it will save you huge amounts of time in future!

Try to replace

M[i]=t;
M[i]=M[j];
t=M[j];

with

t=M[i];
M[i]=M[j];
M[j]=t;

[Edit]
Add this

cout << __TIMESTAMP__ << endl;

it will tell when the program was compiled. It allow you to see if the program you run is the one with corrections.

Think I would change your bubbling

... left out the entry for size and values entered

...

bool fBubble = false;
do{
    fBubble = false;
    for (int i = 0; i < n - 1; i++) {
        for (int j = i + 1; j < n; j++) {
            //
            if (M[j] < M[i]) {   // is position j LE position i
                int t = M[j];       // get the smaller
                M[j] = M[i];
                M[i] = t;
                fBubble = true; // changed
            }
        }
    }
} while (fBubble);
//
for (int i = 0; i < n; i++) {
    cout << M[i] << "\t";
}

would like to add about debugging, it is a simple process and can save time worrying about code