What's the OS?
Could be third party app overriding the shortcuts - I find this on Mac OS only and Windows can be fine.
I've only experienced it on Mac OS.
Start in Safe Mode on the Mac and launch indesign - see if it persists.
If it does then it's a third party app overriding the keyboard.
You're not the first to notice the Shift key not working. There have been other reports.
Personally - I'd revert back to a previous version if the rest of the post fails for you.
Rollback to a previous InDeisgn version unitl fixes for 19.0 are available.
https://helpx.adobe.com/download-install/using/install-previous-version.html#:~:text=Open%20the%20Creative%20Cloud%20desktop,down%20list%2C%20select%20Other%20Versions.
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Other potential fixes
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
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Report bugs
https://www.adobe.com/products/wishform.html