Welcome to CN!
I am very familiar with your 10" scope as I had one, and I am also very familiar with your 30mm eyepiece as I still have one.
When you try to focus, are you finding that the focuser draw tube is not coming out enough to reach focus? This is a common thing to happen, not so much because of a problem with the telescope or eyepiece, but the telescope itself is the same one made by GSO for photo so it is built with photo in mind. The situation for us using eyepieces is the draw tube needs to come out more so eyepieces will focus.
DHEB made the right suggestion in getting an extension tube. However, there is a very quick and easy way to verify that the draw tube needing to come out more is the solution! With the 30mm eyepiece in place & the draw tube out all the way, loosen the eyepiece locking set screw & slowly pull out the eyepiece and see if this bring the object into focus. If it does then a short extension tube is the easiest solution.
That it is a fast focal ratio scope is irrelevant & a Barlow is not a help. Actually understanding the quirks of photo vs visual in the fabrication of mass production scopes helps solve a simple situation.
Malay, you will often also find big differences in the focusing position for different eyepieces. Some will require more out-travel of the draw tube other eyepieces more in-travel. More out-travel is easy to solve if like you the draw tube doesn't come out enough. More in-travel is more difficult to resolve. But let's do this simple trick first of slowly & carefully pulling out the eyepiece.
Oh, and if the eyepiece does need to come out a little, you can still use the scope this way. Simply tighten the eyepiece locking set screw on the pulled out eyepiece. The scope will still work fine.