The attached report shows that line series are displayed as expected using the provided data - check this screenshot.
You can compare your settings with those in the provided report. The report can be opened with Standalone Designer R1 2017.
Based on the screenshot, we can't really tell what Graph's settings might be wrong and we would need to check the problematic report in order to provide you further suggestions.
You can send the report in a support ticket.
Regards,
Katia
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