I recently started a new server with mods I've used before (the Origins mod), but one (and ONLY one) player on the server is having an issue with not being able to place any blocks and other functions like using a fishing rod. However, they can still click in their inventory, so it's not a mouse issue.
We've tried lots of different things, including oping them (we're good friends and I trusted them, but it didn't work), changing their origin, and having them uninstall and reinstall the mods. Any ideas for what could be causing the issue?