Sorry this question isn't really for Getting Started Forum, but there was no Nintex for SharePoint. Only Nintex for Office 365.
Anyone seen this error before? For a SQL Request action on a Nintex Form (classic) when testing I get...
Unable to obtain master key.
Guessing Master key to access Secure Store Service to get target application ID...
Solved! Go to Solution.
Worked this one out. Was a SharePoint 2016 bug with Secure Store Service and updating/refreshing the master key.
The action calls the secure store web service which tries to get update/refresh the key and fails when it can't.