Which product are you using?
PDF.js Express Viewer
PDF.js Express Version
Detailed description of issue
When using the viewer in React and hosting the viewer static through Apache in the root directory, the watermarks will not go away. I also tried to host it through a Nodejs Express deployment and that didnt work either.
I verified that Im getting a 200 response on the call to auth.pdfjs.express, @pdftron/pdfjs-express-viewer is being used and the key being used is definitely setup on the right domain name.
Im not sure how the license verification system works internally so Im out of ideas as to whats going on.