I can also start the videos on my end directly in your post, though i know from the Onboard vs. Real life thread that the forums can behave really odd with too many video posts on one page, you usually have to wait a bit until all the elements of the page have refreshed fully.
updates to your browser, higher levels of tracking protection, adblockers etc can all have an impact on embedded media. If you've had any of those things change between them working and not, double check that your browser settings are not overly restrictive (in most browsers this can also be site specific)