We failed in building our project with the Doconut Professional License. Please view information of the building project in images in the link to support our. Thank you.
Can you start by updating to netstandard2.0?
The net Core build is built on NetStandard2.0.
I also got the same error, using .net core 3.1 (mvc), here error image
76edff361bb6c8e891a7.jpg (858.6 KB)
I can still see the old netstandard:
Let me know how it goes after you change that.