Reactivation (noun)

1. The act of reactivating something that has become inactive.
2. The restoration of something to an active state.

Origin:

Late 19th century: from re- + activation.

Examples:

1. The reactivation of the dormant volcano was a cause for concern.
2. The reactivation of the power plant was a major accomplishment for the engineering team.
3. The reactivation of the patient's immune system was an important step in the recovery process.
4. The reactivation of the treaty between the two countries was a positive development.
5. The reactivation of the subscription was a simple process that only took a few clicks.