There's currently an issue with new unit unlocks, which is causing them not to become available immediately after earning the final part. The Game Team is working on a solution, but in the meantime, players can get the unlock to appear by finishing any ongoing upgrade progress in the Academy. Once that action is completed, the newly earned unit should become available.

Currently, this only appears to be affecting unique units unlocked by earning parts, but if you encounter this with other units, please let Customer Support know.