in my case it was an error (wrong charcter of end of line) in the file /etc/pulse/daemon.conf at the end of file:
wrong:
default-fragments = 5\ndefault-fragment-size-msec = 2\n
correct:
default-fragments = 5
default-fragment-size-msec = 2
I have the same problem. The player is no longer displayed in the spotify list somtimes already after a view minutes.
My Pi is over LAN connected on the same hub like my pioneer receiver with „spotify connect“. The pioneer is always displayed in the spotify list.
Is there a log file to check the spotify connect player on the pi, so that you can see what is happen?