Hi Kim,
First sorry for my english cause it’s not my mother language. I’ve max2play v2.40 on a rpi3.
I had the same problem with shairport. For the automatic switch between shairport and squeeze lite i typed the ip adress of my squeeze box server (on my synology nas) without any extension. 192.168.1.56 for example without :9000 or 9090 at the end and it worked. I checked that on my squeeze box server the command line was accessible via the 9090 port. Now everything is working fine for the automatic switch between squeezelite and shairport.
Hope that it’ll help others.