You could look into using the Wait action as a way to achieve this. Use the wait action after the “Campaign Activated” trigger to wait 2 days. Once the two days have passed, your workflow should invoke the necessary APIs to see if any action has been taken. If no action has been taken, then email the reviewer.
If you need a follow up email if no action is taken after a few more days, then you could call out to an external trigger workflow that also has a wait step. This external trigger workflow would perform the same steps to check if there is activity or not. You could probably use this API to get the campaign activity: list-identity-certifications | SailPoint Developer Community
flowchart TD
1[Campaign Activated] --> 2[Wait 2 days]
2 --> 3[Get Campaign Activity]
3 --> 4{Is there activity?}
4 -->|Yes| 5[End Workflow]
4 -->|No| 6[Send Reminder Email]
6 --> 7[End Workflow]