namepatternPolicy.json

{
    "properties": {
        "displayName": "must match name pattern",
        "description": "name pattern must be this",
        "mode": "all"
        "parameters": {
            "type": "String",
            "metadata": {
                "description": "pattern name can include ? for letters, # for numbers"
            }
        }
    },
    "policyRule" {
        "if": {
            "not": {
                "field": "name",
                "match": "[parameters('namePattern')]"
            }
        },
        "then": {
            "effect": "deny"
        }
    }
}

There is a comma missing after "mode":"all"
and a colon after "policyRule"