Using the debug_mode, you could use the “inspect” functionality on the bottom right of the screen which allows you to manually type in the name of any element you want to inspect.
Type in the name of the button, if there is an “(invisible)” next to the name of the element, this means that the element has been ordered no to be visible.
The inspect tool will help you find the root cause and it will also tell you if there are any conditionals which are making the element not visible.
It might be that you accidentally unselected “This element is visible on page load” in the layout tab of the element’s property editor.
If the element is technically set to be visible, but you still can’t see it, it might be that you set the height or width of the element to be too small so its not actually displaying correctly.