Why is the Online Monitoring Window Not Displaying After Logging into TwinCAT3, with Variables Showing Normally in the Variable Area but Not in the Program Area?

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 After logging into TwinCAT3, the Online monitoring window fails to display, while the variable area remains functional for monitoring. However, the program area does not show the current values of the variables.


PQUESTION  1:

If the program logs in but the online values of variables are not displayed in either the variable area or the program area, it is likely that the main logic (MAIN/PRG) has not been added to the Task. You may notice that although the status is logged in, there is no variable monitoring window.




Resolution: Add the currently running MAIN/PRG into the PlcTask.

1.Locate the PlcTask of the current PLC project, right-click, and select "Add Existing Item".


2.In the Input Assistant window that pops up, select the desired Main/PRG to add.


3.After adding, you need to reactivate the project, and then it will display normally.


PQUESTION  2:
As shown in the figure below, the variable area is displaying normally, but the program area does not show the actual status and values.

Solution: The issue is often caused by the lack of the "Enable Online" checkbox being selected in the TwinCAT 3 settings. Checking this box will resolve the issue.

  1. Locate the "Tools" menu at the top of the TwinCAT 3 software, click on it, and then select "Options."

  2. In the newly popped-up window, on the left panel, scroll down to find and expand the following options sequentially:

    1. TwinCAT
      • PLC Environment
        • Text Editor

    Once you have expanded the "Text Editor" option, you can proceed with the next steps to enable online monitoring.


  3. After clicking on "Text Editor," in the right-hand interface, select the "Monitoring" tab. Then, check the box next to "Enable Inline" in the first row and click "OK" to apply the changes.


  4. After enabling it, the display should function normally.