Can't indent bullet point lists in PowerPoint for Mac

If I insert a text box into a slide and create a bullet point list, I am unable to indent sub-bullet text. However, I am able to indent non-bullet point text. I am also able to indent a bullet point list if I put list in the default body text box (from the presentation master template). It is only if I manually insert a text box and try to do a list. I've had this problem for months and it's really annoying. I'm currently running Version 16.12

Is anyone else having this problem?