I'm also getting this error

Try closing you browser and opening it again, it worked for me.

Thanks, that worked for me as well. Regards,

I've run into this issue also using Nintex Workflow for O365.  I couldn't save changes to a workflow, so I lost changes.  I had to close the browser and reopen the workflow.

I wonder if when this happens if you could take an immediate export of the workflow.  Then close and reopen the workflow, and import the workflow from the export.  Would the changes be present then?

I found a solution that has been working for me.  If you get the "Invalid JWT token" message, keep the workflow you're trying to save/publish open.  Open up another browser tab/window, then open up a new workflow in designer mode.  Once you've done that, go back to the original workflow and try to save/publish it again.

thanks, I almost thought there was no solution as a standard "timeout",

your trick saved me from not losing my changes Eric Rhodes, as I didn't save the workflow for a few minutes.

Glad it helped you out, Francois.