Dell Latitude E5430 fn+f5 touchpad toggle on or off keys not working

Hello, as I've read throughout the forum, I've found that touchpad issues are common, until one got to me.....

I've a Latitude E5430;not much, OS Windows 10, and I recently started using a wired mouse instead of the touchpad. Well, before I first used my mouse, the touchpad toggle on/off shortcut keys 'fn+f5' worked fine. I could disable the touchpad if I didn't need it and was only using the keyboard for typing.

Since the first time I plugged in my mouse, the 'fn+f5' touchpad toggle on/off key  doesn't seem to respond, I thought maybe because the mouse was plugged in that didn't work, so I unplugged the mouse and did the same, but still didn't work.

The other 'fn' shortcut keys work, such as the 'fn+f1' puts the system to sleep and other keys do work fine. The touchpad toggle on/off key only seems to have an issue.

What's the solution?