find my mac turned on via icloud settings, but isn't actually activated (activation lock shows as DISABLED)
posting this in case it can help someone else.
tl;dr: try putting the mac in recovery mode, run disk utility/first aid. it might do the trick.
the longer post:
i've got a macbook air m3, and had to turn off find my for an apple-approved replacement of the screen/top case. when i got it back, i turned find my back on, and noticed the next day it wasn't showing in the device list on my account, or in find my.
i did everything i could find suggested online - a) turned find my off, logged out of the laptop, restarted the machine. b) deleted the relevant find my .plist file (and did the whole logging out/restarting/etc.). c) deleted the find my cache folders. none of it worked for me.
text chat help sent me to phone help who immediately elevated the issue, as it seems to be popping up and they don't know what's causing it. helpdesk person walked through everything i'd done, and then suggested disk utility/first aid. that did the trick.
good luck, if this is happening to you.