If these shortcut keys do have custom functions, make sure to delete them if you wish to use copy/paste between projects. That is, Command + C and Command + V (on Mac) or Control + C and Control + V (on Windows) have their default functions and aren't overridden with custom shortcut keys. You don't have a system preference set up on your computer that overrides the default copy/paste function.
You're copying the element from the actual project in the Designer and not from read-only mode.If you're receiving either of these errors: "couldn't read native clipboard data" or "clipboard is empty", check the following: You also can't copy from projects located in 2 different accounts. Important: You can't copy from projects in read-only mode. You can also undo the paste action by pressing Command + Z (on Mac) or Control + Z (on Windows). Paste into your element with Command + V (on Mac) or Control + V (on Windows).Go to the second project, and select the element you want to paste into.Copy an element from one project with Command + C (on Mac) or Control + C (on Windows).To reuse elements and components in another project: All nested elements, styles, assets, settings, and interactions are retained. You can copy any element or group of elements from any of your projects and paste them into another project.