I was having the same issue as this guy here (Change default size of Player in Video Lightbox)
I fixed it using the solution provided on that question HOWEVER, it only works when I visit the ‘published’ site through webflow. When I download the code and upload to my web server, the page ignores the code and continues to size the vimeo player too small.
Any idea as to why it works on webflow publishing, but not on my webserver?
Best way to see the problem is, first click on this link which is the published site on webflows server: WEBFLOW VERSION
Then click this link which is hosted on my server (following an export of code): MY HOST VERSION
Scroll down to the video, hit play and you’ll see what I mean.
Here is my site Read-Only: LINK