Samsung A40 mobile help?

I've just bought myself a new Samsung A40 to replace my Galaxy S6 Edge which no longer holds a charge for more than a few hours and was looking a little worse for wear.

I love the A40, does everything I need, however, one thing is bugging me.

When the phone is not being used and the screen is blank I'd like to be able to display the time without unlocking it.

I'm not talking about the always on display, the A40 doesn't support that.

On the S6 if you ran a finger down the edge it showed the time. I thought the A40 could be set up to show the time with a single screen tap, a double tap turns the unlock screen on.

What's really bugging me is that on several occasions I've taken the phone out of my pocket and the time was displayed briefly then turns off. I just can't make it do this to order!!!! :mad:

What am I missing?

Help?