I'm guessing those are both in PDF format. Does your Firefox have problems opening, displaying, or printing other PDFs, or only those?

If necessary, you can switch Firefox from displaying PDFs in a tab to opening them in your external PDF reader. This article would have the steps for that: View PDF files using Firefox’s built-in viewer.

By the way, the current version of Firefox is 69.0.3.

Thank you. The forms that come up for Ebay are not PDF format. On this problem FF install PDF forms do come up. Since I have had the issue I have updated FF at a careful rate and am now at 69.0.3. Same problem with Ebay packing lists and labels. The older FF version PC has no problems. Still I believe the issue may be in Options Settings, but have no clue as I have tried many alternative settings. Am wondering if a backup of my FF profile and reinstall is worth effort, but PDF not the issue. Thx Agn.

Have you tried the printer "reset" described in this article: Fix printing problems in Firefox?

Followed article, made resets. Same issue: Ebay packing list or label print locks Firefox. Other site forms and pages print fine... Still scratching my head.

Something must be different there.

Are the problem pages popups that open the print dialog automatically? If so, please cancel that print dialog. Give the page a few seconds to settle, and then try Ctrl+P.

Alternately, do the problem pages have a frame around the content? You can tell because when you right-click a framed page, there's an extra "This Frame" on the context menu. The This Frame flyout has a print command specific to the framed content.