What should you do to fix the video not found error?
In addition, another common issue may also happen.
According to Windows 10 users, there is a problem when playing HTML5 videos in a web online window.

The detailed fault signal is HTML5: Video file not found.
This may happen because your surfing app doesnt support HTML5 videos or there is a web page backend issue.
Fortunately, you’re free to follow these solutions below to easily fix HTML video not found.

Sometimes the web client can automatically update.
But when getting the HTML5 error, check it manually.
If you are using Chrome, hit the three-dot menu, go toHelp > About Google Chrome.
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If you see theUpdate Google Chromebutton, click it.
If not, the online window is up to date.
Clean Cookies and Caches
Caches and cookies can help your online window to run fast.
Take Chrome as an example:
Step 1: nudge the three-dot menu and chooseSettings.
Step 2: ClickClear browsing datafrom thePrivacy and securitysection.
Step 3: SetTime range, choose what you want to clear, and clickClear data.
it’s possible for you to ping the developer of the website to install HTML5 supporting codecs.
So, you’re able to also have a try.
Step 1: In Chrome, go to the three-dot menu and chooseSettings.
Step 2: After clickingAdvanced, deactivate the option ofUse hardware acceleration when available.
Take it easy and this post is helpful for you.
You should easily get rid of the issue after trying these solutions above.
Just have a try!