[cypher]

How long is it since you separated them? It can take some a good couple of weeks or even more to settle & adjust to both a new home & being separated & it is often the more dominant one that takes longer to adjust.
If it hasn’t been that long yet & he does appear to be eating & drinking ok then I wouldn’t worry too much, just give him time, keep talking to him gently even if he doesn’t come out so he can get used to you being around.
Keep cleaning to a minimum, spot clean pee as & when you need to but otherwise don’t do anything for at least a month then just so partial cleans if needed & don’t change anything in the cage & he should settle in & gain confidence soon.