Many bloggers have asked why they cannot upload video via Blogger post editor anymore? Or they ask, what happened to the "filmstrip icon" which I believe is the Blogger video upload icon at the end of the toolbar you see in the screen shot below:

Blogger's toolbar with video upload icon

In practically every case, I have found that the reason their "filmstrip icon" disappeared is because they are using the new updated post editor which do not provide for video upload.

The solution is simple. Just go to SETTINGS > BASIC (the Basic tab is the very first "sub-tab" for SETTINGS which you will be in once you click the SETTINGS tab) and scroll to the bottom of the page. There you will see the options to select the new updated post editor or the old post editor:

Blogger radio buttons to select new updated post editor or old post editor

Select the old post editor, save, go to your post editor and there you will see your "filmstrip icon".

Note: Many also asked after uploading a video via Blogger's video upload icon, where is the video stored, meaning, where is it accessible (like when you upload a video to Youtube, then anyone can view the video or get the embed code at Youtube)? The answer according to a Blogger Employee is,
it "disappear into a deep black hole" meaning you will not get anything like uploading to Youtube.