indesign file, some pages hidden

There was a Show Spread/Hide Spread feature introduced in InDesign 2024 but that works differently. You can still can visually see the pages, but they don't export/print.

Is this the only file this happens to, then there is a good possibility that this file has corruption. As @Eugene Tyson  suggests try saving as IDML: File > Save As > InDesign CS4 or Later [IDML]. Then try opening the IDML file back in InDesign.

If this happens with other files, you may need to restore your InDesign preferences and caches. Here's how:

https://www.rockymountaintraining.com/adobe-indesign-rebuilding-preferences-cache/

Doesn't sound ideal.
Can you let us know your OS version and your version of InDesign?

I think InDesign has added a hide page feature, which I'm not fully familiar with - but doesn't sound like what is going on here, as the other pages disappear when you click on them - sounds like unwanted behaviour

Here are some things to try:

If a document is not behaving well then try 

File>Export 

Choose IDML

Open the IDML in InDesign
Save the file as a new InDesign file with a new name
See if the issue persists.

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Try resetting your preferences:

Windows: Start InDesign, and then press Shift+Ctrl+Alt. Click Yes when asked if you want to delete preference files.
macOS: While pressing Shift+Option+Command+Control, start InDesign. Click Yes when asked if you want to delete preference files.
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