Sadly, I no longer believe this tree is alive. There is plenty of sun and no new leaves at all. Moss has covered the soil and something new is growing and I have no idea what it is. Just posting in case there may still be hope - or anyone recognises the mysterious new plant? I have no idea where it came from.

It’s dead. If you would have followed the advice it might have had a chance. Misting is a myth, it doesn’t increase humidity around the tree.
The plant that is growing is just weed.
If you are interested in bonsai, buy something that is native to your region and place it outside.