Unlike previous connection versions, you cannot pause your v5 by pressing A and B simultaneously.
To pause your v5, you must go to the television option (the middle option on the bottom of the screen) and press 'B'. Then press 'A' until the arrow is next to the 'Travel Show' option. Now choose 'B'. Wait a moment, and the options 'Go!' and 'Cancel' will appear on the screen. Press the 'A' button until an arrow appears next to the 'Go!' option. Then press B.
While your tamagotchi is in travel mode, it will not lose any hearts and it will be exactly the same as you left it. It functions exactly the same as the pause option.
To unpause your tamagotchi (or to exit Travel Mode), press C. You will then see "Come back?" and the options "Yes" and "No" on the screen. Press the A button until an arrow appears next to "Yes". Then press B. "Sure?" will appear on the screen. Press the A button an arrow appears next to "Yes.". You will then see your tamagotchis unlocking the door to their house.
Congratulations, you just successfully paused and unpaused your v5!