Card (new) visual stopped working in service

When I realised the fix might be ages I didn't want to leave my clients without their key daily report so decided to ivnestigate myself.  I stepped through recreating the cards from scratch step-by-step to identify what setting might be causing the issue.  Guess what - couldn't repro the issue, got the cards working exactly as before.  Deleted the problem ones and reinstated.  Go figure