Had this or a similar issue on a Pixel 7 on stable 2025112101.
I think it's because I didn't log in immediately after booting, and the screen had turned off. Nothing I did would allow the keyboard to pop back onto the screen after I woke up the phone.
Terrified, I rebooted. When it started up again, I immediately tried to log in as soon as I could, and the keyboard popped up. Whew.