This app was mentioned in 2 comments, with an average of 1.00 upvote
OK, you have a Japanese Pixel 4.
You should find an 'Osaifu Keitai' application in the list of installed applications. From there, try to install the standalone Mobile Suica application, or do it from the Play Store (https://play.google.com/store/apps/details?id=com.mobilesuica.msb.android): once set up, you can then manage it from Google Pay.
If you don't see the Osaifu Keitai application, check that you have not modified the phone or unlocked the bootloader. On the Pixel 3 it is possible to use Osaifu Keitai with a rooted device, and it should be possible on the Pixel 4, but you should rule this out first.
The Osaifu Keitai application can be downloaded at https://play.google.com/store/apps/details?id=com.felicanetworks.mfm.main but it is not something that you should need to install yourself as it is a factory-installed application; its presence in the Play Store is only to allow it to be updated.
Failing all of these, reset the phone to factory defaults, and if you still cannot complete the setup or see the Osaifu Keitai application, you should request a replacement: it is possible that the phone was not properly provisioned at the factory.
Hmm how about Japan specific?
Can you download mobile suica for instance?