Divya Thakur commented
That error message indicates that there was a problem accessing your Creative Cloud account, which is necessary to share a prototype. Can you please try the following?
1. Close XD
2. Open the Creative Cloud desktop application by clicking the Creative Cloud icon in the menu bar.
3. If you are prompted to Sign In, please do so with your Creative Cloud username and password. Otherwise, click the gear icon on the top-right, Preferences..., Sign Out, and then Sign In.
4. After signing in, launch XD.
5. Re-open your document and try sharing again.
Hopefully that should clear it up.