Q.Acer palmatum firehlow
Hi dear all
I live in a top 3rd floor near the woods of Zollikerberg in Zurich Switzerland. In summer it is very hot and in winter is very snowy this balcony/terrasse.
I planted the tree last September and it lost imediately all the leaves.
I pruned it in autumn.
It survived the winter.
And now I was expecting it to come back. But while it is not dead, it also doesn’t let the leaves grow.
What shall I do?

Follow a regular watering schedule during the first growing season to establish a deep, extensive root system. Watering can be reduced after establishment.
Feed before new growth begins in spring. Pruning time: late winter to early spring.
You will need a shade to part shade location and may need to provide shelter from wind.
You will need to add extra insulation in a container planting.
It's possible some of the roots have died off.
Check the branches; do they bend or snap off.
Also do a bark scratch test.
https://www.gardeningknowhow.com/ornamental/trees/tgen/tree-scratch-test.htm