cannot run any spark code from notebook with starter pool and default workspace

Hi bruceOkallau,

Thank you for contacting the Microsoft Fabric Community Forum.

Based on my understanding, the error SparkSettingsInvalidAutoscaleNodeSize – Invalid NodeSize value: Medium for autoscale limit 2 on Fabric F64 might be caused by a configuration mismatch in the Starter Spark pool following multiple capacity upgrades. Starter pools in Microsoft Fabric are system managed with fixed node size and autoscale settings. In rare cases, the pool metadata does not refresh automatically to reflect the current capacity SKU, causing Spark session validation to fail before any code executes. This is why even a simple import fails.

Please follow the workaround below which may help resolve the issue:

1. Create and attach a custom Spark pool with an F64 compatible node size and enable autoscale.

If you prefer to continue using the Starter pool, please raise a Microsoft Fabric support ticket so that the backend Starter pool configuration can be realigned with the F64 capacity using the link:Microsoft Fabric Support and Status | Microsoft Fabric

For your reference, please find the links below:
Apache Spark compute for Data Engineering and Data Science - Microsoft Fabric | Microsoft Learn
Configure and manage starter pools in Fabric Spark. - Microsoft Fabric | Microsoft Learn
Create custom Apache Spark pools in Fabric - Microsoft Fabric | Microsoft Learn

We hope this information helps to resolve the issue. Should you have any further queries, please feel free to contact the Microsoft Fabric community.

Thank you.