Same here ... I noticed that the failure came after the update to 6.1.14 update on my websites...
Tried to deactivate the module after exporting token with settings, and delete all tables and data in db for WF, and then deleted the module from the system . Reinstalled and exported the former settings..and it worked ..no problems with the err msg anymore.... Did the same on 3 sites and all is good now... dont know if it was just a lucky incident, but it surely worked for me :D