Mickey Mouse

If Mickey Mouse or Minnie Mouse doesn't speak

You might need to download their voices. 

1. Connect your Apple Watch to a trusted Wi-Fi network, then place your Apple Watch on its charger.
2. Wait for about fifteen minutes, then tap the screen again. 

If you still don’t hear their voices, remove the watch face, then add it again: 

1. On your Apple Watch, firmly press the display. 
2. Swipe up on the Mickey Mouse or Minnie Mouse watch face, then tap Remove. 
3. Swipe left until you see , then tap . 
4. Turn the Digital Crown, then tap Mickey Mouse or Minnie Mouse to add the face back.
5. Tap the screen to try to hear the time.

If you still need help, contact Apple Support. 

For more info, see here:https://support.apple.com/en-us/HT207194

Swipe up on your Watch face and make sure you don't have Theater Mode or Airplane Mode on. If you recently updated your Watch try resetting it by pressing in the crown and side button until you see the Apple logo, then release both.

See this information from the Apple Watch User Guide,

Mickey Mouse and Minnie Mouse

Let Mickey Mouse or Minnie Mouse give you a whimsical view of the time—their arms rotate to indicate the hours and minutes, while their feet tap out each second.

Raise your wrist and tap the watch face to hear Mickey Mouse or Minnie Mouse tell you the time.

Choose whether your character speaks the time: Open the Apple Watch app on your iPhone, tap My Watch, tap Sounds & Haptics, then tap Tap to Speak Time. You don’t hear the voice if your Apple Watch is in silent mode—to turn silent mode on or off, swipe up from the bottom of the watch face to open Control Center, then tap bell icon.

Is tap to speak turned on?

iPhone>My Watch>Sounds & Haptics>Tap to Speak Time>

This should be toggled on.

Randy-12 Just gave you the solution.

I would suggest you reset your watch. Press the crown and side button in until the Apple logo appears. Then try it. Also check your Watch is updated 5.2 and your iPhone is running iOS 12.2