Paypal Here app not communicating with card reader

[mgpoole]

Using Android, when I use a sideloader url to send an invoice to the Papal Here app, the app works as expected except that it does not display the amount payable on the screen of the (black) card reader. If a card is inserted it then displays 0.00 and triggers an error in the app. If the sale is cleared using the app, the amount payable then appears on the cardreader screen, but is no longer displayed in the app.
If the app is used alone everything works as normal but of course this makes integration with my POS application impossible.
I have experimented with a basic android app, sending a variety of url examples and with the web example from here-sideloader-api-samples/web/ but always with the same result.
I also tried resetting the card reader and reinstalling the updates.
I would be interested to know if other people who use the sideloader are having the same problem.