We've checked this issue with Truelayer.

Certain features are only available to Barclays app users after 10 days of registering for Barclays Mobile Banking.

If you're attempting to use specific features, like linking your accounts to another app like Updraft via Open Banking within those 10 days, you'll receive an OBA19 or OBA28 error codes.
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If the device you're using changes, you'll also have to wait for another 10 days before being able to use the features related to Open Banking.