Ironix,
A summary slide uses all the titles in your presentation. That is, all the
titles in placeholders, not if you draw a textbox yourself and type a title
in it.
To get a summary slide go to Slide sorter view, select all the slides you
want to make a summary of and click on the button summary slide which should
be on the slide sorter toolbar, 3rd button from the left.

Per PowerPoint help:

Add a summary slide to your presentation  

If you want to include a summary of the key points in your Microsoft
PowerPoint presentation, you can use Slide Sorter view to easily create a
single slide that presents a list of selected slide titles.

On the View menu, click Slide Sorter.
In Slide Sorter view, hold down CTRL while you click the slides that have
titles that you want to include in your summary slide.
Tip  Include only the slide titles that best summarize your presentation.

On the Slide Sorter toolbar (toolbar: A bar with buttons and options that
you use to carry out commands. To display a toolbar, press ALT and then
SHIFT+F10.), click Summary Slide  .
If the Slide Sorter toolbar is hidden, on the View menu, click Toolbars, and
then click Slide Sorter.

The summary slide is created and added to your presentation.