I think I recognize the issue. I saw this reported on Roll20 Discord. The dice that should show in chat are images, hosted on Imgur. The UK is blocking Imgur. A community character sheet coder has to fix it by moving the images to another image hosting service preferably Roll20's github. If you can find-contact the sheet's author/coder, or if not then ask on here for someone else to step up and make the necessary changes. A user on here called Vince knows how to do that.