Hi there, hoppers!
When you change your exchange within the same template this error can sometimes come up.
Your hopper retrieves chart data from the current selected exchange. If you still have position from a different exchange, this error will show. It means your Hopper is trying to pull chart data for these old positions that can now not be retrieved. The solution is to remove these position from your hopper and use the synchronize tool to check for unsynchronized positions.