re-download os from 2014

Apple has made it extremely difficult to download older versions of macOS. Since Apple has removed macOS purchase history from the App Store I'm not aware of any way to directly download Mavericks. The oldest version of macOS which can be currently downloaded from Apple is macOS 10.11 El Capitan.

This Apple article provides information on downloading macOS 10.11 through 10.15 as well as how to create a bootable macOS USB installer:

https://support.apple.com/en-us/HT201372

If you are currently running Mavericks on the computer, then boot into Recovery Mode using Command + R.

Otherwise you will need to contact Apple Support directly (link is available at the top right of this page).

What OS is your mac running at the moment, if it is running El Capitan or earlier the App Store Purchased section should still show any OS you had previously downloaded, this should include Mavericks.

In October Apple re-released a downloadable copy of Yosemite which was the next OS after Mavericks, if you are interested you can get it here. How to upgrade to OS X Yosemite – Apple Support otherwise read the link provided by HWTech.

It may be possible that if you have a nearby Apple Retail Store they may help you out with Mavericks if you provide a USB for them to put it on. They may just give you the Install Mac OS X Mavericks.app, you can take that home and use https://diskmakerx.com/download/ to make a bootable installer, select the correct version for Mavericks.

What is the reason for wanting Mavericks?