Forms not downloading when using Firefox browser

Firefox has its own default PDF viewer. This can sometimes be problematic and not allow Adobe PDFs to generate automatically. Click the menu icon that looks like three horizontal, stacked bars in the top, right corner of the browser, or click Tools in the top, left menu bar in the browser, then click Options. Click Applications in the left side menu, and locate “Portable Document Format (PDF)” in the list that displays. If it shows "Use Firefox PDF viewer" or "Preview in Firefox" to the right, click on where it shows use Firefox PDF or Preview in Firefox, and select Use Adobe Acrobat DC (default) from the drop-down menu icon. You can close the Options tab once done, as there is no Save button.