It didn't work for DD until she was older either.

DO you have a lambswool underthingy for the cot?

is there a problem with her sleeping in the swing ? might be a middle ground between in your arms and in a cot.

I couldn't get either of mine to sleep in the cot as a cot, so maybe i'm not the best person to offer advice anyway
Beside the cost of replacing the batteries lol not really (cause as soon as you turn it off she wakes)