InDesign Paragraph Style won't apply / change

Im hoping someone might be able to help me troubleshoot an InDesign question. Im a beginner-to-intermediate user.

I am unable to apply my Paragraph Style to a number of my text boxes. I have tried holding Opt/Alt while choosing the PS with no luck. I have also checked for local overrides and character styles, and there appear to be none. The fly-out menu from the Paragraph Styles menu is almost all greyed-out, so it won't let me select the Clear Overrides option.

However, when I double-click the text box to go into the frame, I am able to select the text directly and then apply the paragraph style to it directly inside the frame. This seems weird; Im hoping there's a way that I can just select the frames normally and apply a paragraph style as usual.

The text came from a Word document that was flowed into each chapter, if that gives any help.

Looking forward to some advice. Cheers, -Ben