Restoring from Time Machine Backup – Cannot replace Mac HD
My assumption from how your question is worded is that you're trying to recover an entire HD, not just a single file, folder etc.

Instead, to do a full restore of your Mac you need to boot into macOS Recovery and use the Restore from Time Machine Backup utility. 

You may find the following Apple Support resources helpful:


About macOS Recovery
How to move your content to a new Mac
How to use Time Machine to back up or restore your Mac