Ciudadanos won the Catalan election on 21st December last year in conditions which are unlikely to be repeated. The whole unionist movement called out en masse as in none of the previous electoral contests gave them their votes to oust the independence movement from the institutions of Catalonia. The indestructible remained with PSC, who aren't few in Catalonia, almost no one with Albiol's PP. So few that they weren't even able to make a parliamentary group.
Despite its condition as the first party, even if thanks to this exceptional fluke, Rivera and Arrimadas' group didn't even present a candidate for investiture as president in the five months that passed between the election and Quim Torra's appointment. It's true that they didn't have the numbers but, with time, it's been confirmed this wasn't the only reason for their inhibition. Ciudadanos' place isn't really in governing the institutions, but in activism against them all. They didn't go to meet with the Catalan president, they incite their supporters to assault city hall balconies with impunity, they cover violent acts against the independence movement.
They need confrontation to give themselves a place in Catalan public life. Civil confrontation, linguistic confrontation or educational confrontation. That's their modus vivendi. Out of this habitat they flounder in irrelevance.
The criminal complaint they've presented against the speaker of the Catalan Parliament, Roger Torrent, and three other members of its governing Board (Josep Costa and Eusebi Campdepadrós from Junts per Catalunya and Adriana Delgado from Esquerra Republicana) to prosecutors at the High Court of Justice of Catalonia to accept for debate a proposal from CUP restating the independence-minded declaration of 9th November 2015 is going in that direction. Blocking the Parliament's political action and prosecuting Catalan public life.
Going from being the party of 'no' to a non-party. That is, for the moment, Ciudadanos.