I don't know do you got this fixed yet, but what worked for me is this process right here:
Toggle off or disable "automatic updates" and "in-ear detection" on your Pixel Buds setting via Pixel Buds app.
Turn off Bluetooth on your phone, exit and force close all recently used apps, restart it, then turn Bluetooth back on.
Plug your Pixel Buds charging case into a power source using the included USB-A to USB-C cable. Ensure that your Pixel Buds are seated within the charging case and leave the charging case open.
At the back of the charging case, press and hold the pairing button for 30 seconds. When the earbuds status light stops blinking, let go of the pairing button.
The earbuds status light will blink white and orange until the reset is complete and then start blinking white to indicate that your Pixel Buds are ready to be paired.
Once done, try pairing them again with your phone, then re-enable in-ear detection and automatic updates.
Try playing music, making calls or using Google Assistant for 15 minutes to see the results
https://www.reddit.com/r/pixelbuds/comments/gd3mlh/comment/fw3m6rx/
reddit見到,你睇下有冇用