Generated PDF didn't show images in header

Hi,
I created a sales invoice and try to take pdf of that invoice. But at the time of pdf generation the image in letterhead didn’t display. But in print preview there have image. I added host_name in site_config.json. But still it doesn’t display image.Anyone know why?

Thanks

Are you working on server side setup or local setup ?

Try this on server side in site_config.json
“host_name”:“http://localhost”

Solved. First I hosted on digital ocean server. Now I changed to linode server and it’s working.I think may be server problem.