MakerBot Print is our newest print-prepration software, which supports native CAD files and STL assemblies,
allows you to interact with all your printers via the Cloud, and many other exciting new features.

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Yeah, you will want to use the version of ArduinoJson mentioned in the Readme.md file. You have probably loaded the 6.X BETA version.
Remove the BETA version and load: ArduinoJson version 5.13.X.