I've stopped using the Concentration script, as there is definitely an issue with it, likely from an update to Roll20 since the script was created. It looks like Robin developed the script 4 years ago and hasn't been active on Roll20 for a couple years. Some scripts will have issues from time to time, and the only thing to do is restart the API console. It's the VTT version of 'Did you try turning it off and on again?" Your players don't need to reload the VTT page to restart the API console -- you as GM just need to do that from the API Scripts page. You should take a look at CombatMaster - Victor took Robin's ideas from Concentration, Combat Tracker, and Status Info and combined them into Combat Master. So it's a huge script with a lot of functionality, and a bit of a learning curve, but it will likely work better for you, and it's still being actively worked and improved. Other than that, if you want help troubleshooting a specific issue, you need to explain what's happening in the game, what troubleshooting steps you've taken, show screenshots, and/or post any errors from the API Output Console so someone can help diagnose the issue.