Hi there,
I'm sorry to hear that you're having an issue with your AirPods Pro 2nd Gen in the latest AirPods Beta, 6A262e. It sounds like your Transparency mode is not working on the right AirPod, but it is working when you use Conversation Boost. This is definitely a strange issue, and I'm not sure what could be causing it.
However, I can offer you some troubleshooting steps that you can try:
Reset your AirPods. This is a good first step to try when you're having any kind of problem with your AirPods. To reset your AirPods, put them in their charging case and close the lid. Then, press and hold the button on the back of the case for 15 seconds, until the light flashes amber. Once the light flashes amber, release the button.
Update your AirPods firmware. Make sure that your AirPods are running the latest firmware. To check for updates, put your AirPods in their charging case and connect them to your iPhone or iPad. Then, open the Settings app and go to Bluetooth. Tap on the i icon next to your AirPods and then tap on Firmware Version. If there is an update available, your iPhone or iPad will automatically download and install it.
Pair your AirPods with a different device. If you're still having problems with your AirPods, try pairing them with a different device. This will help you to rule out any problems with your iPhone or iPad.
If you've tried all of these steps and you're still having problems, then you may need to contact Apple Support for help. They will be able to investigate the issue further and offer you more specific troubleshooting steps.