A new law has been passed which from the 8th May 2021 makes it illegal to sleep in a motorhome overnight outside designated motorhome areas like campsites or camper parks.
It always used to be that you could park anywhere that any other vehicle could park quite legally and it didn't matter if anyone slept in the vehicle overnight.
There were various differences between 'parking' and 'camping' - steps out, chairs out etc But from the 8th of May just parking overnight with the intention of sleeping will be considered camping and will be illegal.
More details (in Spanish) here https://www.onroadmagazine.com/valencia-prohibe-la-pernocta-de-autocaravanas/
If it ain't broke..... Don't fix it!