I have been struggling with a sin for quite some time now, but have had little success in quitting. It leaves me wondering why Allah SWT has not granted me a way out of it. I've struggled for years and have tried so many different things. Am I doing something wrong on my part that may block me from receiving Allah's help? I'm confused.

The fault is not with Allah as you said He is not granting a way out but we must stop the sin by having firm resolve in not doing it. Study the outcomes of the sins in this world as well as their outcomes in the next. This knowledge will come to your mind when wanting to do that sin and inshallah will refrain you. May Allah help us all.