I had a similar issue, reboot the phone, when it boots up, don't touch the finger print scanner, unlock with code.Installed the ROM with the recommended version of twrp and firmware for sweetin and rooted with magisk agter setup. Everything works fine, safetynet checks but my fingerprint and face unlock works only with apps and not on my lockscreen. Please help.
Give the phone 30 seconds or so to boot, lock phone, finger print scanner then works.
I have to do that every so often.