I am also having this issue. Lastpass Autofill in Chrome doesn't log me into lastpass with biometrics but going to the lastpass app directly works fine. Once logged in, autofill works.
Pixel 4XL w/ face unlock.
For what it's worth, I've been having the exact same issue for some time - fingerprint works fine in the LastPass app, then then autofill works fine in Chrome on my Pixel 3a XL, which has a fingerprint reader on the back. Fingerprint fails when prompted in Chrome. Please fix.
Same issue, Pixel 5 with latest Android 11 updates. Really glad to have found this thread confirming that it's not just an issue due to some incorrect setting on my side. As others may have mentioned, I don't see this issue (even with the latest LastPass app version) on my older Pixel 2 phone, which suggests it may be an issue with the latest Android update(s), which the Pixel 2 didn't get due to end-of-life.
LastPass really needs to get this fixed ASAP, or at least get some update to threads like this one confirming it as a known issue and giving some sense of timing for a fix when it's available.