Hi, thank you for contacting JustAnswer.com. My name is Russell. I will do my best to provide the right answer to your question.
So first off: Can you tell yet, whether the problem is
1. a lack of a scroll bar at times ?
2. the pen doesn't work, on some screens at least, or maybe all the time ??
3. it just doesn't scroll in FB even when there's a scroll bar ?
Android OS is different from Windows.
That may be all there is to it.
As for the scroll bar being very narrow... you can change the size of screen elements, in Windows. But other things than the scroll bar may change size also.
So, with that in mind, would you like to try to change settings to enlarge the scroll bar?
And also... is what you are trying to do with the FB timeline, similar to simply holding down the mouse button with the mouse pointer amid the timeline stuff on the screen, then dragging the mouse downward without letting go, so as to scroll the screen downward through the timeline by doing a massive select, in the downward direction, so that the 'blue highlighted' selected portion forces the screen to scroll downward?
When you try that with the pen, does the blue highlighting appear at all?
OK. Do you need advice on (I think the settings are in the Display app in the Control Panel app set) ...how to make items on the screen like the scrollbar, bigger?
If not, if you're done with the case, please rate my answer and my efforts to help. A five-star rating would best express appreciation of my care with this case.