Starting with the release of Strategy ONE (March 2024), dossiers are also known as dashboards.
An image with a URL of http://localhost:8080/image/1.png is visible in a dossier, but disappears when the dossier is exported to a PDF. Similarly, HTML containers with a URL from localhost will not load the web page from localhost.

This may occur because the URL is resolved to a different machine after the export. Loop-back addresses, like localhost or 127.0.0.1, always point to the local machine where the URL is proceeded. Usually, the PDF Export Service is running on a different machine from the end users'. Therefore, such URLs are only accessible to the author of the dossier. If you change to a different machine and open the dossier, the image won't load and will disappear on PDF files.
Your localhost may refer to the correct machine of the PDF Export Service, but still, the image will not successfully load. This is because, since Strategy 2019 Update 1, the PDF Export Service cannot process local requests. Any URL of localhost or loop-back addresses will be denied.
You can move the image to
./image/folderof Strategy Web or Strategy Library. The current web application is in the whitelist.