Where are my marks on the new revision?

Open the drawing from Current revisions.
If the revision before this one has marks, the bar under the sheet says so by name, for example Rev C carries 2 marks. Open it takes you to that sheet, with the marks on it.
Read them there, on the sheet they were made on. The date and the name are still on every line.
If what you found is still true of the new revision, mark the new sheet too.
That is a new action on a drawing you actually looked at. This is the reason it does not happen automatically.
A superseded sheet still opens and still holds its marks. Nothing is removed when a new revision arrives.

Worth knowing

This is on purpose. Nothing is missing. A mark carried forward would say somebody found that on a sheet they never opened, and a later reader is entitled to believe them. Marking the new sheet takes one press, and it means what it says.