Revision Schedule Issue on the Sheets
In Revit, you can choose which revisions need to be showed up on each sheet using “Revisions on Sheet” on the properties. However, sometimes some revisions are greyed out, so you cannot uncheck those revisions on the sheet. This is happening because revision clouds of those revisions are already placed on the sheet, so you have to remove or hide those revision clouds on the sheet not to show on the revision schedule.
If you cannot find revision clouds on the sheet, you have to go to View tab > Sheet Composition panel and click on Sheet Issue/Revisions icon.
On the popup, change the Show field to “Cloud and Tag” and click “OK”. Then, those clouds will be visible on the sheet.
Once you delete or hide the revision clouds on the sheet, the revision will be gone from the revision schedule.