Warning for \usr\share\grommunio-common\nginx.conf: the "listen ... http2" directive is deprecated, use the "http2" directive instead. So replace
server {
server_name _;
listen [::]:443 ssl http2 default_server;
listen 443 ssl http2 default_server;
...
with
server {
server_name _;
listen [::]:443 ssl default_server;
listen 443 ssl default_server;
http2 on;
...
