This account is locked and can't be used (AppleID is not active)

(Before posting links please know that the general Apple Support webpage leads right back to this error message.)

Today I was helping an apple iphone & old ipad owner, who is unable to get any support for this issue. She gets the following messages:

Iphone Forgot Password Menu: "Cannot verify identity - this AppleID is not active"

Apple Support > Request to Unlock your Account webpage: "This account is locked and can't be used"

I was struck that there was no further options allowed. This is a new one for me.

Can anyone suggest how / why this might have happened? (If not a solution?)

(FYI the account / device owner said at one point they were talking to apple phone support, but then at some point, the rep cut them off abruptly and said there was nothing to be done in this case, as if they had seen something negative in the record. But I can't confirm this or that they were actually talking to apple.)