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You must explicitly allow read and write access to the Lango user on restricted content you want to translate. Otherwise, Lango will not be able to translate the page, and you will get a similar error:
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How to solve the issue
Open the page restrictions panel
Search for Lango User and select “Can edit” permission
Apply the new configuration
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Need help, or do you want to suggest a new feature?
Our support is available 24/7 with an 8h SLA. Contact us at our customer support portal or by email at support@adapps.atlassian.net. We will be happy to answer all your questions.
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