I’m encountering a persistent issue when trying to launch Dynamo through Revit 2026 after upgrading to the Autodesk 2026 suite. Every time I try to open it, I get the following error message:
System.IO.FileLoadException: Could not load file or assembly ‘RestSharp, Version=112.0.0.0, Culture=neutral, PublicKeyToken=598062e77f9f5f75’. Could not load or find a specific file.
(FileNotFoundException: Object not found)
What I’ve already tried:
Clean uninstall and reinstall of both Revit and Dynamo.
Tried installing and reinstalling both via direct installer and via package-based deployment.
Removed all user packages (the ‘packages’ folder is empty).
Verified ‘RestSharp.dll’:
The correct version (112.0.0.0) is present and matches the one used in Dynamo Core. Replacing or copying it from other machines did not resolve the issue.
Tried running as Administrator and verified Windows file permissions and unblock settings.
Tested same installation on a different machine → Works perfectly.
Tested on a different user account on the same machine → Issue persists.
System, Revit, and Dynamo are fully up to date.
Dynamo Core (Standalone): I manually downloaded Dynamo Core 3.4.1 and 3.5, and both launch without any issues, suggesting the problem is specific to the Revit-integrated Dynamo environment.
System Information:
OS: Windows 11 Pro (Version 23H2) – Build 22631.5189
Revit version: 2026
Dynamo version: Default version bundled with Revit 2026
Hardware:
CPU: Intel Core i7-12700 (12th Gen)
RAM: 32 GB
GPU: NVIDIA T1000 8GB + Intel UHD Graphics 770
Has anyone encountered this or have any insights? Any help or direction would be much appreciated! I’m happy to provide additional logs or test further if needed.
Basically Revit requires any 3rd party component which uses rest sharp to be version 112, but many add-ins are using another build, including some early builds of Autodesk provided add-ins which predate the release of Revit 2026.
Start by disabling ALL Revit add-ins and then all Dynamo packages/extensions.
Restore Revit add-ins back in a binary search method until you identify the conflict or fail to reproduce it. If you find the conflict update it or reach out to the manufacturer to get it updated.
If you don’t find a conflict, move into restoring Dynamo packages/extensions in a binary search until you identify the conflict. If you find a conflicting package update it or reach out to the provider to get it updated.
When you identify the conflict please post back here so the community knows what the likely suspects are. My current list consists only of a pre-release version of the Forma add-in for Revit.
Thank you so much for your detailed response. It was spot on and incredibly helpful!
Following your recommendation, I disabled all Revit add-ins using the Add-ins Manager. After that, Dynamo launched successfully for the first time in days
I then began re-enabling the add-ins one by one, testing Dynamo after each activation to isolate the conflict
At first, I suspected PyRevit (given it’s third-party and loads slightly slower), but I uninstalled, reinstalled, and re-enabled it, and Dynamo still worked fine
Next, I tested the Autodesk Forma add-in. As soon as I re-enabled it, the RestSharp error returned immediately when trying to launch Dynamo
I disabled Forma again and re-enabled all other add-ins, and Dynamo continued working without issues. So, it looks like the conflict was indeed caused by the Autodesk Forma add-in (likely an early build not yet updated for compatibility with Revit 2026’s requirement for RestSharp version 112)
Thanks again for the clear and structured troubleshooting approach, it really saved me hours of frustration! I hope this helps others in the community as well
