Undefined appkey error could be the cause of a common error when you’re loading or submitting the app offline. To solve the problem you need to publish the web page and access it online or use direct URL of the DataPage.
You may also see this error if you’re using direct URL of a Report DataPage when you leave the results page for a few hours and then attempt to go to the Details page. The reason is that record’s session expires and cause the error message when you attempt to go to the record Details page. To avoid this situation, use embed deployment method or create custom details link which remains permanent. See how.