So the problem here is that you have disabled the ID input. When a filed is disabled, it's not posted. Your update query receives an empty ID and there for does not execute the save. What you should do is make the input hidden instead.
<label for="id">ID: <?php echo $row;?></label> <input type="text" id="id" name="id" value="<?php echo $row;?>" style="display:none">
On a side not, You should really use the browser developper tools. When you send a POST/GET request, it's saved in the network tab. You can use that to see the submitted values in the request headers and there for, you would have seen that id is missing and that's why your query is not working ;-)