Why is a "Failure - refresh_token is invalid" window appearing?
If the following Failure - Refresh_token is invalid window appears when you launch Easy MTD VAT or after you click the Get button, the refresh token that was applied to Easy MTD VAT when authority was granted to it by HMRC is no longer valid. Refresh tokens naturally expire after a certain number of days (this is a HMRC policy).
To stop the error from occurring, the process of granting authority to Easy MTD VAT will need to be performed again. Start this process by clicking the Authority button in Easy MTD VAT (your Government Gateway ID and password will be required during the process of granting authority).
To start seeing a rather less cryptic message for this error, update to the latest version of Easy MTD VAT.