Everything I have read, you need the original certificate, no copies. Are you from the US?
We took the original certificate for boarding and a copy when we’re in port, as some places required to see our vax card.
Princess website:
Europe
We will accept the EU digital Covid certificate.
For international, non-UK guests, the following formats are acceptable proofs of full vaccination: Digital or paper records, or QR codes, showing the vaccine type, the date of each vaccine administered, the individual’s name and date of birth or other identifier.