The following error is thrown when you are deploying a workflow from a .kspx package:
The field '<field name>' used in the Event Item on the '<event name>' Server Event does not exist in the environment library. Create the required field where necessary. ---> System.Exception: The following errors occurred while compiling the process (with framework version 4.6.1)
This error may also be thrown in the InstallerTrace logs when you are trying to install K2 Five on a new server while referencing a K2 database from another environment.
This error is trying to tell you that your workflow is referencing an environment field that is not present in the current K2 environment where you are trying to deploy the workflow.
To resolve this, go to K2 Management > Environment Library, select your default Environment Library, and make sure the environment field mentioned in the error message exists. If not, just create the environment field in your default Environment Library.
Once you have done that, redeploy your .kspx package again.
If you are getting this error in your InstallerTrace logs when running an installation of K2 Five, then you may not have a K2 Management page that you can access to add the missing environment field. In that case, you can log a support case with Nintex Support, inform support the issue you are facing, and send a copy of your InstallerTrace. Support will guide you through on how to add the environment field into the K2 database.