Hello @jozo,
I got that error too - what a hassle to find out the reason. It is caused by the GRPC backend not speaking ssl - so you have to use a plaintext connection. Just replace grpc_pass grpcs://10.0.0.2:33060; with grpc_pass grpc://10.0.0.2:33060; in your nginx config.
@zayn you might want to replace that line in your documentation?
https://pydio.com/en/docs/kb/deployment/running-cells-behind-nginx-reverse-proxy
Kind regards
Franz