There is a declaration of conformity from Jolla for both the original Jolla phone and the tablet. There is none for the Jolla C which means that for the time being, it may not be marked with the CE mark and may not be sold in the EU.

https://jolla.com/legal/

The problem probably is that Jolla simply isn't the manufacturer of the Jolla C (not built to Jolla specs like the other devices) and hasn't tested the devices for conformity yet.