Get the player to make a roll and then press the 'up' key in chat. This will give the roll's macro which you can assess for issues, post here if in doubt. Also ensure that their character sheet is filled out correctly. And, as Silvyre rightly suggests, hover over the rolls to take a look at the tooltip to see if anything strange is happening there. To compare get someone whose rolls aren't behaving in this way to do the same roll from their sheet and cross check the macros, tool tips and sheet attributes to look for anomalies. Lastly assign control of that sheet to someone else and get them to run the problematic rolls to see if they get a result. And if all of that fails to suggest a solution: Can you please follow Steps 1-3 of our Solving Technical Issues wiki page, taking special care to temporarily disable all browser add-ons and extensions, temporarily pause your anti-virus, and try switching browsers (for Chrome/Firefox specific issues) to see if one of those components is causing the problem. If all of that fails, please follow Step 4 , including providing all of the necessary information, so that we can further assist you.