Hi there

This error can be caused by enabled ASP.NET Impersonation Authentication for Autodiscover under the K2 site.

View the following link to solve this problem

https://help.k2.com/support-services/kbt168424?source=PC_Pro%2526version=published

After doing what the link above instructs, clear cache and delete cookies then restart the browser.

Let me know if it helps.
If not please let me know of the k2 version you are using

Regards
Huli

Good day AaronAbe

Try to apply the latest CU and FixPack.

(Also see the following:

‘Editing a workflow, an error occurs: "Internal Server Error 500: Object reference not set to an.."’: https://community.k2.com/t5/K2-Five/Editing-a-workflow-an-error-occurs-quot-Internal-Server-Error/ta-p/102123,

Code Fix: An error occurs when editing a workflow deployed from a K2 Package when the workflow has a field referencing a SmartObject: https://help.k2.com/kb002229.)

Best,

Sunrise

Hello  @AaronAbe ,

If you are using K2 Five(5.2):

1. Ensure you have K2 Five (5.2) installed.


2. Download the K2 Five (5.2) FP33 from https://portal.k2.com/products/k2five5-2fix-pack33


3. Install the K2 Five (5.2) FP33 to apply the fix.


4. Refresh the browser.


5. Re-load the workflow.

Reference:https://help.k2.com/kb003116

-Follow the manual installation "Configuring TLS 1.2", part "Minimum Requirement" of this:

https://help.k2.com/kb002500

I hope this helps