Thanks for the report @yasu1111 , but I'm not able to reproduce the issue.
I accessed the link and the video played with no issues as presented in the image below.

Tested with:
Browser / Version: Firefox Nightly Mobile 66.0a1 (2019-01-02)
Operating System: Huawei P10 (Android 8.0) - 1080 x 1920 pixels (~432 ppi pixel density)

@yasu1111 , could you please update to the latest Firefox version, and give it another try?
Also could you try clearing cache/data/cookies, disable Ad-blocker (if available) and check again?

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