Trills over several bars don't work

Hi everyone,
I don't understand how we are supposed to create trills over several bars.

In the picture, I give to my clarinet a trill over 8 beats (it's 4/4 bar). When I play the sound, the trill works perfectly on the 4 first beats (with a cool acceleration effect, as intended), but stops after the first bar. The note is a constant Eb instead of a trill.
When I add a trill to the second-bar note, what I get is a clutter : the second trill acts like no trill was running before.