Strange message pop up

When one of my players makes a roll in game this happens: It doesn't matter if it's from a sheet or using basic roll functions in the chat this always happens and only for him. We have also tested on a different campaign and it happens again.

I think your player will need to go through our  guide to   Solving Technical Issues . Step 1: Make sure to use the right browser Please check if these issues persist when using both Chrome  and  Firefox. Step 2: Ensure that there are no extensions/addons interfering with Roll20 Please disable  all  add-ons/extensions  and  anti-virus programs. Step 3: Clear your cache If none of the above succeeds, please thoroughly work through  Step 4 .  (Don't forget the complete Console Log!)