We have a single machine that fails to launch Dynamo from Revit.
The machine is running Revit 2026.4.1 freshly installed.
The error is system.io.filenotfoundexception
The screenshot below shows the exact error report.
There are no Revit addins loaded.
There are no Dynamo packages loaded.
Based on the assembly ‘system.runtime’ I have guessed that means .NET 10 - that has been reinstalled fresh.
Other machines with the same build of Revit 2026 (and our usual office addins - Pyrevit, Ideate, Xrev) all load Dynamo correctly.
The difference in machine builds is that the offending machine (mine) has Visual Studio 2022/2026 installed and doesn’t have piles of Adobe rubbish.
Revit 2025 (and older) on the offending machine loads Dynamo correctly, it is only Revit 2026 that fails to load.
Revit has been uninstalled / reinstalled completely, but the problem persists.
I’m at my wits end.
Has anyone else seen this error and know of a fix?
I’m hoping it’s not Visual Studio, surely I can’t be the only person running VS on the same machine as Dynamo 
I am running revit 2026 and visual studio 2022, but i have also side installed .net 10 SDK/runtimes to be able to utilise .net10 in visual studio 2022 so i can get my revit addin ready for revit 2027.
I will say Revit 2026 is built of .net8 and .net10 only came in for Autodesk 2027 software and Dynamo V4 generally in respects to revit. Though there is a couple of exemptions of dynamo versions that have been updated to .net10 which can be found here - .NET Compatibility | Dynamo
Revit host integration versioning can be found here - Host Integration Map | Dynamo
Though I would suggest you post your revit and dynamo journals/logs and dynamo settings file here as well because these will highlight any possible hidden issue.
Revit journal file attached. I’m no expert on journal files, but I can see the command that starts Dynamo from the ribbon button, and then… nothing. There doesn’t appear to be any entry that gives a status, good or bad, for Dynamo.
There is no folder for Dynamo 3.6 under \AppData\Roaming\Dynamo\Dynamo Revit and thus no logs for Dynamo. I don’t know of anywhere else that Dynamo stores logs.
journal.0101.txt (383.3 KB)
Does Dynamo crash or Revit?
If Dynamo we need the Dynamo log more than the Revit journal.
There are no logs from Dynamo.
I have looked in \AppData\Roaming\Dynamo\Dynamo Revit, and there isn’t even a folder for v3.6 which is I think what R2026 uses.
I am unaware of any other locations that Dynamo saves log files.
Revit doesn’t crash, just Dynamo.
As a near last effort to self fix, try deleting any other folders in the 2026 directory - one of them might be getting picked up in migration.
It could also be attempting to migrate preferences from a 4.x instance (my suspicion). 2026 is in .net 8 so .net 10 isn’t the root cause. I also have all the Dynamos and all he .net versions so I can confirm it is a you thing. You can try on that system as another user to help rule out a migration issue.
If both of those fail, reach out to my colleagues in support by starting a new ticket in the accounts portal at manage.autodesk.com.
Hi Jacob,
Thanks for assisting.
Which folder are you referring to in ‘the 2026 directory’?
I take it not the Revit 2026 install folder
Also, this is probably not a Dynamo 4.x issue as I don’t have Revit 2027 installed.
The 3.5 or 3.4 folder. 4.0 could come from sandbox or other tools as well, but if you haven’t used it then that’s likely not the cause.
