Class in Custom JAR library not recognized by the Notebook but available by classloader

Hi Faber1975 ,
Thanks for reaching out to Microsoft Fabric Community.

Thanks for the update and for sharing the details.

It looks like the issue might have been related to the notebook environment not being fully initialized when you first tried to access the custom JAR. Sometimes, classes from a JAR may be available to the classloader but not immediately usable through direct import statements until the session is fully ready. This could explain why it started working correctly later without any changes.

Just as a general note - when working with custom libraries, it's a good idea to make sure any required dependencies are also uploaded, especially if they’re not already part of the environment. While this may not have been the cause in your case, it can help avoid similar issues in other scenarios.

Glad to hear it’s working now. If the issue happens again, restarting the notebook session usually helps.

Since the issue is resolved, please consider closing this by marking your reply as the accepted solution. This will help others who might face a similar situation.

Thanks again.