Collabora online fails on shared host installation of nextcloud 16

Hi, I employed nc on a shared host with ~15 users.
Up to now, Collabora was working smoothly out-of-the-box.
Now, after updating to nc 16 and Collabora 3.3.10, I get the error
“Failed to load Collabora Online - please try again late”
What I understand from my online research, the Collabora server is not found. Do I need to install and configure it separately now (wasn’t this working before?). Or is there a new port used? Obviously, I cannot open additional ports/ run docker on a shared host installation.
Any ideas how to get this running again?
Thanks, Robert