In Galatians 2:6-10 we see how Paul, Barnabas, and Titus’ gospel was the same one the other apostles, such as Peter, had been preaching. The encouragement here is we can rest confidently in knowing the gospel has not changed! The good news of Jesus is still the same as in the early church - and it still has the same power!
The question is: if the gospel does not have the same power in your life as before, has it changed? Or have you changed? Have you added something to it? Or are you living in the past, closed to God doing anything new in your life?