Why will a case not close?

Because a required step is still missing its evidence — and the database is what says no.

When you try to close a check that still has a required step without evidence, it is refused, and the refusal names how many steps are outstanding.

What matters is where that refusal lives. It is not the button being greyed out; it is a trigger in the database. So the same answer comes back through the API, through a direct connection, and to an administrator. Turning off the interface does not turn off the rule.

That is the whole reason the record is worth anything a year later. A closed check is a closed check because it could not have been closed any other way.

A step is missing its evidence: Capture what it asks for. The refusal tells you how many are left.
Every step is done but it still refuses: Some checks need independent acceptance — somebody who did not perform the work has to accept it first.
You are an administrator and it still refuses: That is the design. Nobody outranks the gate.