Can't indent bullet point lists in PowerPoint for Mac

Okay I just came across this problem for Powerpoint 16.57 on my Macbook. I did a lot of digging and I found that the only solution to this problem, if the tab button is not working on bullet points to make sub-bullet points, is to open up a new Powerpoint presentation and copy it onto the new one. Essentially, you are merging the 2 Powerpoints. To do this:

1. Open up a new blank Powerpoint presentation 
2. On the new Powerpoint presentation, click on the HOME tab
3. On the HOME tab, you should see the option to add a NEW SLIDE, next to the NEW SLIDE, there should be a drop down arrow, click the drop down arrow and select 'Reuse Slides...'
4. Once you click the 'Reuse Slides...' option, it should bring you to your files, so locate and select the Powerpoint file that you want to merge (the Powerpoint where the indent bullet point feature does not work). Click OK after that and the 2 Powerpoints should have merged

This should solve the bullet point not indenting when clicking the TAB key