The exact model number would help. My guess is that your machine, like most laptops these days, defines the function key row as "smart keys" or similar that makes them do things like increase/decrease screen brightness, volume, or mute, etc. Typically in this case if you hold the Fn key while hitting the corresponding function key it should behave like it used to in the past. Trying Fn+actual function key for the JAWS commands, and seeing if that works, is an easy way to confirm whether or not "smart keys" is active.
This feature can be turned off. Some brands require this to be done in UEFI/BIOS before Windows boots while others have built-in utilities to do it. I think that Dell is one of the latter.
Brian - Windows 10 Home, 64-Bit, Version 1803, Build 17134
The real art of conversation is not only to say the right thing in the right place but to leave unsaid the wrong thing at the tempting moment.
~ Dorothy Nevill