You probably have "Show Edit Pins" set to "Never" at the left-hand side of the Toolbar. Change it to something else to get the pins and lines displayed, but note that changing it to "Auto" will only show the pins and lines when the cursor is on the image, they will be hidden when you if you move the cursor away from the image.
BTW, you said you've just updated to the latest version.....but your screenshot shows an earlier version, so check your Creative Cloud app for updates.
And even if set to 'Never' the keyboard shortcut [H] will Show/Hide the pin & guidelines by toggling the visibility.
Your video indicates that you are mistakenly scrolling down to the BASIC Panel of adjustments where any slider adjustment is 'Global'- affecting the whole image.
You must stay in the Masking panel sliders to only adjust your linear gradient-
And you can invert the Mask to show the mask on un-affected areas.