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vamshib1880
New Participant
September 22, 2026
Question

Error navigating to Plan tab inside the application container

I am getting the below error while navigating to the Plan tab inside the application container. 
Any possible solutions or suggestions to fix it.
This issue also not letting me to open the application from designer. 

The System Has Encountered an Error

HTTP Code: 500 APNX-1-4198-000 Error Evaluating UI Expression Expression evaluation error [evaluation ID = e7f4a:bc82f] : Cannot invoke "com.appiancorp.core.expr.portable.Value.getType()" because "value" is null

 

 

4 replies

stefanhelzle0001
stefanhelzle0001
Brainy
September 22, 2026

What kind of environment is this? For Appian cloud, I suggest to open a support case.

    karthikeyp990198
    karthikeyp990198
    New Participant
    September 22, 2026

    Would recommend you to check after sometime or open a support case 

      aadityas208231
      New Participant
      September 29, 2026

      I’m curious to know whether you created or added the site using any external MCP agent. I’m asking because I once asked the Dev MCP to create a site and add pages to it, and it accidentally added more than 10 pages to the site, which isn’t allowed in Appian and resulted in a similar error.

      When configuring the site manually in Appian, it doesn’t allow us to add more than 10 pages. However, it seems that the MCP was able to bypass this restriction and create more than 10 pages. I wanted to understand if you experienced something similar or used any external MCP agent to create the site.

      mathieud0001
      mathieud0001
      Genius
      September 29, 2026

      Is there anything in the logs? I would also suggest you open a support case.

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