YouTube clips not playing in mobile browser

Not sure where else to post this, but having some weirdness when posting youtube clips lately. I normally just paste the embed code in html editor as I like the 420/315 dimensions. Usually works like a charm.

But now when I do it, the clips will not show up in mobile browsers.

I recently tried using jetpack short codes, and that ceases playability altogether when I go for those dimensions.

I can’t use the default size because it knocks out my sidebars.

This only seems to be an issue with newer clips as the code has gotten much bigger. Here’s a clip I tried using without success:

<object width="420" height="315" classid="clsid:d27cdb6e-ae6d-11cf-96b8-444553540000" codebase="https://download.macromedia.com/pub/shockwave/cabs/flash/swflash.cab#version=6,0,40,0"><param name="allowFullScreen" value="true" /><param name="allowscriptaccess" value="always" /><param name="src" value="//www.youtube.com/v/0inzO5y6Sck?hl=en_US&version=3&rel=0" /><param name="allowfullscreen" value="true" /><embed width="420" height="315" type="application/x-shockwave-flash" src="//www.youtube.com/v/0inzO5y6Sck?hl=en_US&version=3&rel=0" allowFullScreen="true" allowscriptaccess="always" allowfullscreen="true" /></object>

And here’s an older clip which works fine, with much shorter and different coding:

<iframe src="https://www.youtube.com/embed/Y0mo8Rmu6AI?rel=0" height="315" width="420" allowfullscreen="" frameborder="0"></iframe>

Any idea how to fix? Here’s my current post which shows up fine as long as you’re not on a mobile browser, in which case it is just a big blank spot:

https://smellslikeinfinitesadness.com/40-most-underrated-tv-shows-of-all-time-part-1/

[Please use the code buttons or backticks when posting code on these forums]