The faucet that control the shower and the spout in the bath tub cannot be turned to have hot water. Before that was OK, the handle of the faucet can be turned almost 360 degree and had hot water. But after it was dismantled and re-assembled back, the handle can only be turned about 180 degree and has no hot water. The brand is Symmons. The faucet in the sink in the same room has hot water.
So, what is the problem and how can it be fixed?
Thank you very much.

You have not said whether cold water runs from the faucet. I would say that since it has been disassembled and reassembled this has been done incorrectly and the tap is not actually open. When reassembling the tap it must be fully open before reassembling it

What brand is your tub/shower valve? Back to you, Tom