I've purchased a music album but now iTunes can't find its location. Can I download it again?

Presumably you are seeing broken links ! ? Delete the entry completely from iTunes then try re-downloading.

Download past purchases from iTunes in the Cloud - https://support.apple.com/en-us/HT201272 - "With iTunes in the Cloud, you can access your past purchases from the iTunes Store, App Store, iBooks Store, and Mac App Store." - enabled with iTunes 10.3 and newer; not all media formats are available in all countries (see: iTunes in the Cloud, iTunes Match, and iTunes Radio availability by country - https://support.apple.com/kb/HT204632);