Child theme not working after moving to new host

I recently changed web hosts and migrated my WordPress sites to the new host. I backed up the databases and uploaded them there. I even backed up my wp-content folders. Some of these sites were running child themes and when I first opened those sites at the new host, the themes were broken. I put everything on the server exactly as it was with the old host. One of my sites gives me this error:

Nirvana Child Theme The parent theme is missing. Please install the “Nirvana” parent theme.

Other than this problem, everything works as it should.