Note, the Verifone P400 is no longer available for purchase.
If your previously-registered Verifone P400 card reader unexpectedly loses its registration:
In the Dashboard or through the API, re-register the reader.
Discover the reader.
Connect the application to the reader.
Two actions cause a Verifone P400 reader to lose its registration:
You are using Stripe Connect and the platform account deletes this reader via the API, or
You connect the reader to another Stripe account.
If a Verifone P400 loses its registration, reader discovery no longer returns the reader until you register the reader again.
Connecting to the Verifone P400 (Stripe Docs)