No longer able to swipe up to ping my phone. How do I fix this?

This button (see picture)

Use Control Center on Apple Watch - Apple Support

Just a quick press and release will bring up the Control Center, just like the previous swipe up displayed for you.

DO NOT hold the button, as that will bring up Emergency services.

If you are having timing issue getting the quick press and release right, then adjust this setting:

Settings -> Accessibility -> Side Button Click Speed

• Default is a fraction of a second
• Slow is within a second
• Slowest is within 2 seconds.

There is one press and release (Control Center)

double press and release (Apple Pay)

press and hold (Emergency Services)

The Control Center access has been relocated. Tap the side button, the flat, oval button next to the Digital Crown.