Adobe CC 2018 won't open my CC 2017 files! how do I get it to work?

How are you transporting them from one machine to another? What happens when you try to open them?

You should be able to simply open any InDesign file from an earlier version with CC 2018. On the other hand, if you want to open a CC 2018 file in an earlier version you'll have to export the file as an IDML file which can then be able to be opened by the earlier versions (you will lose any features unique to the newer program used in your file when opening with an earlier version, however).

If you can't open files made from the earlier version you should first try deleting your InDesign preferences.

To do so:

For Macintosh Users: With InDesign closed Launch a Finder Window in column view and click on your home folder. With the Option Key pressed choose Library from the Finder Go Menu. Within the Library folder find the folder called Preferences and within it find the following two files and delete them: “Adobe InDesign” and “com.adobe.InDesign.plist”. When InDesign is next launched it will create new preference files and the program will be restored to its defaults.

For Windows Users: You can try the quick way of resetting on a PC which is to hold down Ctrl + Alt + Shift when launching InDesign and respond affirmatively when asked if you want to reset. There have been some recent reports that the window asking if you want to reset is not popping up but that the prefs are being reset anyway. If this works great but if it doesn’t you may have to manually delete them.

To do so:

On Windows 7 and above the preference files are hidden. To find them go to the Control Panel and open Folder Options and then click the View tab. Then select “Show hidden files and folders” or “Show hidden files, folders or drive options” in Advanced Settings. Then delete (or rename) the folder at the end of this path: C:\Users\<USER>\AppData\Roaming\Adobe\InDesign\<Version #>\<Language>. Make sure that InDesign is closed when you do this. When you relaunch the program it will create  new preference files and the program will be at its default settings.

The advantage of manually deleting preference files is that after you’ve reset up the program (make sure that no document window is open) to your liking, you can create copies of your personalized “mint” preference files (make sure that you quit the program before copying them—that finalizes your customization) and use them in the future to replace any corrupt versions you may need to delete.

If this does not work you might try uninstalling InDesign using the Creative Cloud Desktop app (click on the "V" to the far right of the program name in Apps and the uninstall option will appear). Then reinstall the program through the desktop app. Make sure that when you reinstall the the option to "Import previous settings and preferences" is unchecked in the Advanced Options which will appear during the install. Installing using this options has contributed to a number of performance problems with CC 2018. Please see: CC 2018 InDesign—Don't Import previous settings and preferences .