I use the same Firefox at home and in office with sync function, but the same online PDF is not opened/displayed properly at home.

This problem came out of no where. I always open online PDF file in the firefox browser, and I have the sync function turned on for everything, so I would expect the firefox should work exactly the same at home and in the office. However, the firefox at home is not displaying online PDF properly, and the same online PDF is displayed just fine in my office. I tested with disabling all add-on, theme and so on, and they didn't fix my PDF displaying problem at home. I can't figure out what happened, please help. Btw, I'm posting this in the office.