Windows 10 - Your phone - Add a phone - Disabled

I have the exact same issue. I found this: https://www.reddit.com/r/Windows10/comments/9pdie4/gpo_that_blocks_access_to_link_phone_in_1809/

Depending on your version of Windows 10, you can either:

1. Edit the local Group Policy (i.e. gpedit.msc) to disable Turn off Microsoft consumer experiences in Computer Configuration -> Administrative Templates -> Windows Components -> Cloud Content (I would also set the User Config local GP the same way) or...
2. Edit the DisableWindowsConsumerFeatures DWORD registry key (set it to 0): Computer\HKEY_LOCAL_MACHINE\SOFTWARE\Policies\Microsoft\Windows\CloudContent