Connecting to an OPC UA Server with Mendix: Connection Success, Read Issues

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Hi everyone, I'm currently working on a project where I need to connect to an OPC UA server. I came across the OPC UA Client Connector on the Mendix Marketplace, which appears to be compatible with Studio Pro version 9.24.35. Reference: Mendix Marketplace - OPC UA Client Connector After following the documentation, I was able to successfully establish a connection to my OPC UA server.     However, I'm facing an issue: I can't read the values of my nodes. I tested the same nodes using UaExpert, and everything works fine there—so the issue doesn't seem to be on the server side. Here’s the error I’m getting when trying to read the values in Mendix:     Has anyone encountered a similar issue or have any idea what might be causing this? Any help or suggestions would be greatly appreciated!
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OPC UA Read Error – Root Causes and Fix Checklist

  • Successful Connection confirms network and authentication are correct.

  • Node ID Format Issue

    • Your current Node ID: ns=1;id=1

    • Recommended format: ns=1;s=MyVariableName or ns=1;i=1

    • Use the same format as in UaExpert (check if it uses string s= or integer i= identifiers).

  • Missing Node or Invalid Path

    • The node might not exist or is inaccessible using the provided ID.

    • Use the Browse feature to locate the exact node structure and confirm ID.

  • Permissions / Access Level

    • Ensure the user credentials used have read access for that node.

    • Some servers require session-level permissions, even if the node is visible in UaExpert.

  • Data Type or Structure

    • Some nodes contain complex or unsupported data types.

    • Test reading a basic scalar node like a Boolean or Int32.

  • Connector Limitation or Bug

    • If the node is valid and readable in other tools, it could be a limitation in the Mendix OPC UA module or how the underlying Eclipse Milo library handles it.

  • Logging and Debugging

    • Enable advanced Mendix logging for OPCUAConnector to get deeper error messages.

    • This will help isolate null exceptions shown in the stack trace.

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