Yeah? so? You have an error in the theme your using, has nothing to do with any other theme.
You just have to find out what that error is and fix it, to find the error you need to look at your php error logs.
You have VPS so you have the error log and I pointed you to a reference link on how to find where that error log is residing.
When you get the error log and look at it, it will show you what php errors you have going on and usually will be something simple like “cannot find function yada yada yada on line #132 in the functions.php” so there’s an excellent lead to figure out what the problem is.