My PID'ed Silvia doesn't produce good espresso anymore after a few months rest

Because my stomach had some problems with coffee, I didn't use my PID'edSilvia the last few months. Until then I usually had good to very good espressos with a nice crema.
This week I wanted to start brewing with her again and at first I did a good cleaning with backflushing. However, although I didn't change anything in my setup, I cannot get good results anymore.
I use the same beans as before that I roasted myself to about the same degree as a few months ago. At first the coffee comes in a steady flow but after about 10 seconds I only get a few drops and there is hardly any crema. Even after changing the grind a few clicks coarser on my Mazzer Mini it doesn't improve.
Could something be wrong with my Silvia as a result of the few months rest ?