Uninstalled and then reinstalled the Nintex Workflow App but there was no change to the issue.

I've contacted Nintex Support - looks like it may be a back-end issue.

I am as well experiencing the same issue.  I'm also seeing weird things with Nintex Forms no longer running custom JavaScript files.  

Hello Warwick,

I got the same problem today with Internet Explorer.

But, you can create your workflow with Google Chrome, Mozilla Firefox or Edge.

Since the workflow is created, you can still modify it with IE.

I hope it works for you, too.

I wish that were the case for me it doesn't work in Chrome, Firefox, or IE.

I think the best way to start investigation from in such abnormal behavior is to go to https://status.nintex.com and check if services are working properly.

Had de the same issue Friday around 12:00 CET, later on it was gone, suspect it was a platform issue so indeed wise advice to check for the nintex platform status.

If you're still seeing the issue can you please raise with Nintex support.

Unfortunately broken in all browsers, looks to be a backend Nintex/MS integration.

Yeah usually the first place I check, but unfortatly in my experience it's slow to update from both issue present and once fixed. Thanks

Can everyone check if they can view workflow actions in design please? and if so raise a support ticket with Nintex Support. We haven't been able to edit any Nintex Office 365 workflows for nearly 4 days now...

No problem in Europe. I'm working with Designer every day and would have noticed such error . But Nintex components are hosted in many locations, so even though it's working for Europe --> Poland, doesn't mean it's ok elsewhere.

What build version of SharePoint Online is everyone running?  The tenant I'm having problems with is on version 16.0.0.6105. 1205 I know of others on version 16.0.0.6015.1205 that are NOT experiencing problems.  You can get the build version at https://rootsitecollection/_vti_pvt/buildversion.cnf.  I have a support ticket into Nintex and apparently it is an issue with a Microsoft update per them.  So we'll see.

Same issue here, same error and the Workflow name defaults to "New Workflow". Additional notes, none of the browsers work, however I've other site collections that do work. 

-Dottie

Issue now looks to be fixed thankfully after 5 days of not being able to edit any Nintex workflows in our tenant...

This was the answer from Nintex Service Engineer today:

Quoted

I believe the issue that you were experiencing was due to an authentication issue within the SharePoint Online platform. Microsoft is in the process of rolling back this update to clients tenants, and we've been told that the fix should be pushed to all tenants by tomorrow. I will check in with you once we have confirmation that the fix has been fully deployed.

Yes, thanks Microsoft!

Hopefully this post won't need to be referenced again.