Presentation mode not going to full screen

Try resetting your preferences:
The easiest way to reset everything is to delete the InDesign preferences: as soon as InDesign starts to boot hold down Shift, Alt, Ctrl (and Apple/Cmd if working on a Macintosh). A dialog will appear asking to delete the InDesign Preferences, select 'Yes' on this dialog.
Further info and instructions here if needed:
https://helpx.adobe.com/in/indesign/kb/indesign-preferences-support-file-locations.html

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Reinstalling rarely fixes everything - you can do a complete reinstall using the
Creative Cloud Cleaner Tool https://helpx.adobe.com/creative-cloud/kb/cc-cleaner-tool-installation-problems.html

Hi @Freya26792512bqjg,

Is only the presentation shortcut key not working or do you face issues with any other keyboard shortcut also?

Just cross-check which keyboard set you used Edit >> Keyboard Shortcuts >> Set
If the default one is selected then select another set and again select your default one.

You can also check below link questions and answers: https://community.adobe.com/t5/indesign-discussions/indesign-presentation-view-not-working/td-p/9277526

Hi @Freya26792512bqjg,

Thank you for reaching out, and sorry for the trouble. I am unable to reproduce the issue at my end on the windows10 machine. Would you mind telling us the version of InDesign installed and the details of your operating system? Have you set up any custom shortcuts for "Presentation" mode?

We will try our best to help.

Thanks,

Harshika