why won't 10.15.3 install?

Holding shift down before pressing 'install' and continuing to hold shift down until it requested my password worked!

This link works so thanks for posting. The update takes 9 GB so I only had about 5 GB left so that is why it never installed automatically. I delete a pile of junk and installed it from Old Toad's link. Thanks!

What have you tried and what were the results including any error messages you might have gotten.

Also what update are you trying to apply and what system version are you currently running?

Okay so this actually worked for me l cleared my Mac till there was 18gig available and immediately it installed

Sorry, but that is just not enough information in order for us to be able to assist you with a potential solution.

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Have you tried the combo updater mentioned in an earlier post?

Download and run the macOS Catalina 10.15.3 Combo Update.  See if that will work.

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I'm having the same issue. I can't install the macOS Catalina 10.15.3 update. I click "install now", then it immediately says "to update, you must restart your Mac." When I restart, I still get a notification that an update exists and it takes me through the same exact process described above. I'm plugged into power, have waited for it to install overnight multiple days, but same thing.

What OS are you on now?

Could you be trying the 10.15.3 Combo update from 10.14.x???

Care to share what resolved it so that others coming across this issue may find it helpful?

Same problem here, very stubborn. I have Catalina 10.15.1 (19B88), running on MacBook Air (13-inch, 2017). First tried to update straight to 10.15.3. After downloading and preparing the install, and after restarting, nothing changes. Repeated several times. Didn't matter whether I followed the normal procedure through System Preferences or if I downloaded the dmg directly from https://support.apple.com/downloads/macos. Safe Mode also didn't help. I definitely have enough disk space. Then I tried first updating to 10.15.2 before attempting 10.15.3. But I get the exact same behavior with the 10.15.2 update: install package prepares itself and then asks for restart, to no effect. Wasted all morning on this. Any ideas?

That's literally all the information there is. We are on Mac OS, current less this problematic update that simply will not install. Red notification badge on System Preferences icon. Clicks to install update. Computer restarts. Same badge and same update appear. Try again, then again. Take #4. Take #5. I've probably tried six times or more and it just won't install.

Please help.