Unable to play video – error: An error occurred. Please try again

Hi Team,
I have some videos set up in a grid gallery and the lightbox option is checked.
When I click on the video, it opens video play window, but when I click on play button, it shows ‘An error occurred. Please try again later’ (playback id: random numbers). It happening to all my videos.
I’m using the free version and I only have one video grid. You can see issue on this URL: https://bicentenary.in/celebration-glimpses/
I don’t have any google analytics plugins.

If uncheck lightbox option, then if I click on video – it plays sucessfully on youtube site.

Another thing, I can’t select thumbnail pictures when I click on ‘Click here to get video information and thumbnail from youtube’. I get the message that ‘could not find such video’.
If I select custom video thumbnail, it doesn’t show on the webpage. (you can see on the URL that there is no thumbnail.

Can you please help me with this asap?
Thanks in advance.

The page I need help with: [log in to see the link]