Apple Pay disappearing on Apple Watch 7

That should not happen unless you have some snake oil security apps on the iPhone like VPN or Anti-virus.

If unpairing and pairing does not fix it permanently and you have no security apps on the iphone which is updated to iOS16.3.1 then Contact Apple Support

You ought to reach out to Apple Support directly. You should be able to reach them here

Click here > Contact - Official Apple Support

or phone numbers

Click here > Contact Apple for support and service - Apple Support

and or

Genius Bar Reservation and Apple Support Options - Apple

Also recently I had turned on AssistiveTouch in Accessibility. I had turned it off and Apple Pay was not working from the Watch, I turned AssistiveTouch back on then turned OFF the “Confirm With AssistiveTouch”, then turned off AssistiveTouch, and the ApplePay worked again, showing the “Hold Near Reader” when you double tap the side button

The calling the bank thing is a requirement in USA that we don't have in my country UK and also needs to be brought into 21st century.

We use the CVV codes on the cards.

I still have never had apple pay disappear on any device. The only time it was not working on Watch with double click was on the occasion I described where I had been experimenting with assistive touch and left part of it still on.

Bugs tend to affect everyone, this doesn't, it's not a commonly reported problem.

If you want Apple to know

click> https://apple.com/feedback

as they are not here

Describe what you mean by disappearing please.

In Settings, Accessibility, Side Button click speed, have you moved the click speed away from the Default speed? If so move it back to Default.

By the way the Dock you described comes up with a single side button which again suggests your double click may be a bit slow .

If you press the crown and tap on Wallet is Splke Pay there?