yy7d6, You need to read the autorouter details and any PDF docs that they have online regarding the autorouter. I don't know about your particular length rule but 'all' rules are not followed by the autorouter. So I suspect your length rule may be one of the ones the autorouter doesn't follow.
otherwise, have you actually confirmed that your rule is valid and properly formatted (syntax)? Try routing a trace manually and deliberately exceed the rule length, then run the DRC check and confirm that it was caught by the DRC? Then give the router a simple one net task that would exceed the rule length (two pins X + some net length further apart than your rule limit). If it routes it then it obviously doesn't follow the rule, the way you wrote it. I know that a lot of people writing rules have difficulty getting the right syntax or the right qualifiers. Have you thoroughly read the approx. 3 PDF application papers dealing with queries, rules and rules syntax?
You could also post your query to the AD Forum and you will likely get an answer from Altium tech support or other users who have done the very same thing. In this forum there are very few AD users and even fewer that are not hobbiests.
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