# Can't open dynamo in Revit 2021

**URL:** <https://forum.dynamobim.com/t/cant-open-dynamo-in-revit-2021/87040>\
**Category:** Uncategorized\
**Created:** [March 7, 2023, 9:31am UTC](https://forum.dynamobim.com/t/cant-open-dynamo-in-revit-2021/87040 "2023-03-07T09:31:35Z")\
**Posts on this page:** 1\
**Showing post:** 8

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**Author:** ![Kzs\_David](https://avatars.discourse-cdn.com/v4/letter/k/a5b964/32.png) [@Kzs\_David](https://forum.dynamobim.com/u/Kzs_David)\
**Post date:** [March 8, 2023, 3:09am UTC](https://forum.dynamobim.com/t/cant-open-dynamo-in-revit-2021/87040/8 "2023-03-08T03:09:30Z")

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Thank you for your answers, I have solved my problem, here is how I solved it :

1. I first uninstalled the plug-in py.revit I installed. At this time, the problem changed from the message A to the message B.
2. And I try the method provided by others below:  
[If you cannot launch Dynamo in Revit 2021 with NullReference IsOptedIn error](https://forum.dynamobim.com/t/if-you-cannot-launch-dynamo-in-revit-2021-with-nullreference-isoptedin-error/87068/)  
 ![未命名-1](https://us1.discourse-cdn.com/flex022/uploads/dynamobim/original/3X/2/5/25fc6ec205845f57de35d6d8aac4f40de069969e.jpeg)
3. Finally, I can open my Dynamo in revit2021! And I reinstall my py.revit, it works too!

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