Generally speaking, data can be restored and reconstructed in more than 98 % of cases. Conversely, this means that data recovery is not possible in about 2 % of cases.
It depends on the type of storage medium and the actual defect / error. The most common reasons for an unsuccessful data recovery include deleted and overwritten / zeroed files, fatally destroyed magnetic disks on hard drives, trimmed SSDs and fatally rebuilt RAID servers.
In most cases, it is the previous rescue attempts before handing the respective storage medium over to us.