Here's what I've always seen for a video on YouTube that has been viewed. see screenshot You will need to provide evidence of your issue. What do you see in other browsers?

Well, everything seems to be working today. See screenshot.

Hi Jon, Well my issue has surfaced again where videos do not show to be read by changing to the pink color from blue. Here is a screenshot.

I did not understand before what you were referring to stating this is what an already seen video on YouTube looks like for you. I cannot understand your screenshot. Let me know what you think about my screenshot.

Thanks for your recommendation on how to fix this. Dave

PS. The issue only occurs on Firefox, which I use exclusively for YouTube.

I'm sorry, I also meant to also say referencing the screenshot that I sent you, I went to both of those videos and only one shows to be read with the pink color. The other one did not turn pink and remains looking unread. But I have read it and others near it that did not turn to pink.