I've never seen a smartline controller installed. Products seem to be regional. I do know an open zone means there's a bad wire. You'll have to track it down. Look everywhere visually. Did anyone do any digging recently where they may have cut a wire? Are there spare wires you can use? You might have to hire someone to find the problem or run a new wire.
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This is from your manual. Yep confusing.
ZONE XX OPEN:
OUTPUT OPEN CIRCUIT: If a zone exhibits a load that results in a current draw less than 30 mA a zone open fault is created, but operation continues normally. The fault can be manually cleared or will automatically clear if a load exceeding 30 mA is placed on the output and the output turns on successfully. See Section 6.2.1 for instructions on reading actual current outputs.
OUTPUT