TCPDF don't display image with writeHTML

This wasn't your problem, but it's a possible solution for people with a similar issue in the future. Please make sure the HTML attributes have double quotes.

$html = "<img src='...' />"; // This will not work

$html = '<img src="..." />'; // This will work

As things are working locally so you may try changing the image type from png to jpg and check after modifying your code accordingly and uploading the jpg on the server.

You can convert image type "jpg/png" to base64. <img src="data:image/png;base64,iVBORw0KGgoAAAANSUhEUgA...."/> this may help you !