There are more factors that go into buying or refinancing a house then just a good credit score.
People get turned down for any number of reasons. Just a few are because house isn't appraising high enough, the person has too much debt, not enough job time, they could have tax liens and on and on. Some lenders won't approve the loan if the borrower has a large prepayment penalty on their current mortgage or if there is no true benefit to the borrower to refinance.
You don't say who you have been trying to get the refinance with. By law, if you are turned down for a credit, you are supposed to be sent a denial letter telling you why you were denied the loan. Have you not received these letters?
In any case, the best way to get a mortgage, is to find a mortgage broker in your area and let him handle it. You obviously have something in your circumstances keeping you from getting the refinance. A broker can probably help you with whatever it is. Don't go through your bank because banks have much tougher guidelines that they go by. Also, I wouldn't try to go on line and apply for a mortgage either. They won't take the time to help you that a local broker will.
If you get denied again, ask the broker why you have been denied. You need to find out what the problem is, so that you can work on correcting the problem.
I am a mortgage loan processor