The UK Driving Licence generally has a hologram on top of the photo on the ID. This can obscure the photo making the similarity check, that is required to validate the ID, inconclusive. This can be the reason the ID check is failing.
In this instance, we recommend you using a Passport if you have a valid one.
If this is not possible, you can attempt the Driving Licence again by taking a picture of it in a particular angle whereby the reflection of the hologram does not obscure your face in the photo ID.