Microsoft has announced the deprecation of Azure ACS (Access Control Services) for SharePoint Online, effective 2 April 2026. However, we are observing that some SharePoint Online tenants are already experiencing the impact of this deprecation ahead of the official retirement date.
In affected tenants:
- The K2 for SharePoint Registration Wizard fails during registration.
- Active Site Collections fail when trying to ensure the SharePoint token.
- SPFx Migration Tool fails on migrating event receivers.
- The failure presents as an SharePoint Auth Error.
- This appears to be related to ACS-based authentication no longer being accepted in certain SharePoint Online environments.
The recommended solution is to move to the K2 for SharePoint SPFx integration, and migrate existing SharePoint add-in solutions using the released migration tool. (https://help.nintex.com/en-US/K2cloud/userguide/current/Content/K2-for-SharePoint/MigrationTool.htm)
For Nintex K2 Cloud customers:
- A fix was introduced in K2 Cloud U22 Fix Pack 6 to prevent duplicate process instances triggered from the legacy remote event receivers. You can request this fix pack be applied to your K2 Cloud environment through a support ticket.
- The K2 for SharePoint SPFx Migration Tool v1.4 for K2 Cloud has also been released. For more information on migrating your K2 for SharePoint solutions and to download the SPFx migration tool, see the documentation at https://help.nintex.com/en-US/k2cloud/userguide/current/Content/K2-for-SharePoint/MigrationTool.htm
For Nintex K2 Five (on-prem) customers:
- A fix was introduced to configure a setting to correct object reference errors when interacting with ACS on the Registration Wizard and Activate Site Collection K2 pages. These fixes are available in:
* K2 (5.8) Fix Pack 27 (Download here)
* K2 (5.8.1) Fix Pack 14 (Download here)
* K2 (5.9) Fix Pack 04 (Download here) - The K2 for SharePoint SPFx Migration Tool v1.1 for K2 on-prem has also been released. For more information on migrating your K2 for SharePoint solutions and to download the SPFx migration tool, see the documentation at https://help.nintex.com/en-US/nintexautomation/userguide/current/Content/K2-for-SharePoint/MigrationTool.htm
We are continuing to work on fixes to address potential duplicate process instances being triggered from legacy remote event receivers. You can log a support ticket to receive manual workaround procedures if you are impacted.
This post will be updated when additional fixes are available.
Additional FAQ
Q. Does this ACS issue impact customers using Entra ID without SharePoint Online integration? For example, if you use Entra ID as a user directory and have deployed the app to register the integration, will you have to change anything if you do not actually integrate with SharePoint Online?
A. No, if you do not integrate with SharePoint Remote Event Receivers, you should not encounter this issue.