Some sites that serve videos don't provide a download button. Some
don't even allow you to use the Windows right-click menu to download
them that way. However, there are ways around that. They're called
download managers (DM). There are tons of them available and many,
if not most, are free.
I use one called Video DownloadHelper. It's an add-on, aka extension,
to Firefox, but IDK if it's available for other browsers. I've used it for
years and it's rare that it can't download a video. It sometimes even
provides multiple resolutions to download, i.e. 480p, 720p, 1080p, etc.
If you don't use Firefox or you don't want to use Video DownloadHelper,
just go to where your browser serves up add-ons or extensions and
search for download managers or something similar.
As I said earlier, everyone, IMHO, should be using at least one ad/popup
blocker. They are also browser add-ons. Some that I know of are Blur,
Ghostery, Adblocker and Disconnect. They even come built-in to browsers.
Firefox has one built-in. IDK about other browsers. If you use Firefox, you'll
find it under, Options - Privacy and Security.
Now, having said all that, you should know these four things.
Websites can and will change the way they do things and what
they can change is nearly endless. In other words, what worked
yesterday, may not work or work the same way, today. Adaptability
is key.
No one DM will allow you to download every video you run across.
But, you can always use more than one. What one DM won't
download, another may.
The same goes for blockers. No one blocker will stop all popups
and eliminate all trackers. So, it's a good idea to use more than
one.
And, if you ever see a popup start to load, just quickly press
Ctrl+W to instantly shut it down, whether it's a new tab or a new
window.