Certain Imports are only possible using the host ID, rather than the user ID. For instance, I need to unlock over 300 accounts in bulk, but this task can only be completed via the General User Import type using host ID, not user ID. Our school does not assign host IDs, and therefore the only way to unlock the accounts is to manually visit each one.
Previously, we used a username import type to complete this task, but that import type no longer exists.
As a workaround, you can go through the Blackbaud ID authentication page via Enrollment Management and adjust the filter so that inactive accounts are included. From there, you can sort by the warning column and then select in bulk and reactivate.
I'm assuming you're talking about candidates/parents of candidates for a particular entering year but if not, the same thing can be done for other roles through Core -> Security -> Blackbaud ID authentication.