This can happen when the system tries to build/retrieve the pyRuleSet from the D_pzDefaultRuleContext.
If this has a blank value then this can lead to this error.
In order the correct this behaviour amend the Access Group by setting a Default time configuration ruleset version (Advanced tab). This change will require the user to log out/in again in order to pick up the change.
After opening Designer Studio → Application ->Components and creating a new component, adding label and version and attempting to submit resulted in the message “Error- No open ruleset versions available”. This has been resolved by updating pxUpdateRecordInner and pxCreateRecordInner to check for Rule-RuleSet- instead of only looking at Rule-RuleSet-Branch so that a version is not required for ruleset instances themselves.
If you still need help I suggest that you log a New Question as this post has been inactive for almost a year.