Before requesting for a qualified seal, you need to make sure that your service provider is a Qualified Trust Service Provider (QTSP). Further, to be more specific in your seal request, you need to ask for a Qualified Electronic Certificate supported by a Qualified Signature Creation Device (aka QSCD) that can produce Qualified Electronic Seals.
Disclaimer: Please note that the European Commission cannot provide a legally binding interpretation of the EU legislation, as this is the sole competence of the European Court of Justice. Any remarks from the European Commission services are without prejudice to the position the Commission might take should related cases arise in a procedure before the Court of Justice.