Logged in as the user with the issue, lock the project then unlock the project by opening the project in Read/Write mode in either Microsoft Project (MSP) or Open Workbench (OWB).
Detailed steps below:
1. Log in as the user with the issue and navigate to the problem project.
2. From the Project or Tasks tab, click on the 'Open in Scheduler' drop down and open the Project in Read-Write mode in either Microsoft Project or Open Workbench.
3. Once the project opens in the scheduler tool, refresh the PPM project page.
4. You'll see a message that the project is locked in PPM. Click the Unlock button.
5. Now, you should be able to autoschedule/edit the project without any issue.
Note: If the project has been scheduled previously on one scheduler tool, it's not supported to switch to another scheduler tool (IE OWB to MSP) and save the project back to PPM as that can cause data issues, but in the steps above, the project is not being saved back.