Revit cannot run the external application "Pollination.Revit": System.AggregateException

[stolzyhe01 (Hunter Stolzenberg)]

I recently installed the Pollination plugin for Revit to test out the free trial, and was met with this " System.AggregateException" error upon Revit startup.

What could be causing this issue and what can I do about it? From what I could find from other posts, this is likely an AddIn conflict, but I’m not sure how I can find what AddIn is causing it.

[mostapha]

Hi @stolzyhe01, welcome to the forum! You’re right that this is most likely a dependency conflict between the Revit addins. See here for a very similar issue with Nlog.

Revit cannot run the external application

Hi @aislas, This is most likely a conflict issue with another Revit Addin. It looks like an older version of Nlog is loaded. Can you try to add an underscore before the Pollination addin name? See here for more information: In the case of Revit 2023, the path to the file is C:\ProgramData\Autodesk\Revit\Addins\2023\Pollination.Revit.addin.

This topic covers how to deal with disabling them if your conflict was happening because of a different addin.

Installing Pollination 2.338.0 Revit Plug-in for Revit 2025

Thank you for debugging, @srojas92! Let’s see if I can find someone in their company to help us with this. I don’t know if I know anyone, but @ksobon might know someone who can help us. A quick update from one of the customers who has a similar issue: adding an underscore to the front of the Pollination.Revit.addin file will cause it to manifest before CTC tools which prevents the load error. CTC mentions they have already fixed this issue in the 25.3 or higher versions of their plug-in.

[stolzyhe01 (Hunter Stolzenberg)]

I’ve tried a few fixes:

1. Uninstalling CTC tools programs (our company no longer uses them due to FIPS encryption issues)
2. Adding an underscore to the front of the “Pollination.Revit.addin” I’ve located at:
   C:\Program Files\pollination_revit\plugin\2024

If there is a continued conflict with Revit addins, I’m not sure I can follow the same process in Revit 2025 since I am on version 2024.

Perhaps I tried the wrong AddIn file?

[mostapha]

Hi @stolzyhe01,

My suggestion is to temporarily disable all the other addins by renaming the file extension in the folder that you listed except for Pollination Revit. Reopen Revit and see if it works. That will confirm our assumption about dependency conflicts.

Once we know that, we can start looking into the list of the addins that you have and try to find the problematic one.

You only need to make these changes in the folder with the Revit version that you are using. In your case 2024.

[stolzyhe01 (Hunter Stolzenberg)]

Ah, it turns out I renamed the wrong ADDIN file!

I found the Pollination.Revit.addin file located at C:\ProgramData\Autodesk\Revit\Addins\2024, and adding the underscore to this file caused the plugin to load correctly upon Revit startup.

Hopefully this shouldn’t cause any issues with other plugins, there’s a lot that is added by our company that I don’t use or haven’t used yet.

ProgramData is a hidden folder on my PC for some reason, so I was only able to access it by typing the name of the directory itself.

Thanks for the help!