Description of the issue: I will receive pre-roll ads when logged into my main YouTube account. If logged into a secondary account or not logged in, there will be no pre-roll ads displayed. Notably, the ad name is not displayed at the top and the progress bar will appear red (like a normal video) when mousing over the ad.
Exact URL of the website in question: Any YouTube video while logged in.
Does the site function as expected when Shields are turned off? No.
Does the ad appear when using a Private window as well? (yes/no) No, but only if I turn off Shields for youtube.com before opening a private window. If shields are still on, the issue persists when I am logged into my main account. (Note that if I turn shields off, I will receive mid-roll ads instead)
What OS are you using when you see the ad? Windows 10.
Did you try clearing cookies and cache? Look at a similar post I have earlier:
Though his case is iPad OS clearing the browsing history, cookies and cache might ultimately help. Though you may want to make back ups if don’t want to clear all your browsing history.