As Racer said, CH meds, including verapamil, can become less effective over time. Your 240/day verap is essentially the minimum dose, and IR is strongly recommended instead of ER. Yes, you got results from the 240 ER in the past, but IR at a higher level might be needed this time.
In glancing through this thread, I'm not seeing -- or I probably am missing -- mentions of the vitamin D3 regimen, which is a better, and better-for-you, preventive than verap.