Without a reproducer it's hard to tell what exactly caused the issue. I can suggest double check (via console.log) the following:

• data structure passed to series, including data.nodes - it needs to follow the requirements for networkgraph
• depending on the version of Highcharts you are using, ensure you are correctly initialising your modules (see the following article regarding changes with v12: https://www.highcharts.com/docs/getting-started/version-12
• also check how defaultOptions and userOptions are merged - there might be some intentional override of settings causing the issue here

I hope these suggestions help with debugging.

If you're still facing issues, consider creating a minimal reproducible example.