Can only select things with keyboard in finder, trackpad stops working

[Shemluck]

Hi everyone,
As the title suggests I'm having issues using my touchpad when the finder pops up to select or add attachments to emails, or uploads.
It works perfectly at all other times. It is really frustrating as I'm not skilled with using keyboard shortcuts within finder to select items.
Why has this happened and how do I fix it?

HELP PLEASE!

 

[DeltaMac]

So, you can move the cursor, and you can click to select anything that is not emails or uploads?
Or, do you mean that everything else works, but you can't use the trackpad to click or select anything?
Which Mac do you have? I'm assuming you have some type of MacBook. How old is it?

If you are not sure what you have, you can some information under the Apple menu/About This Mac