NFS Server not responding when Mac is mounting

I've setup a NFS Server on a Ubuntu 18.04 machine. The problem is when I mount it on a MacBook Pro, and move files from Mac's disk to the mounted foulder, the system freezes.

Looking at the logs on the server site through vim /var/log/messages i see this error:Dun

lockd: server MacBook-Pro.local not responding, timed out

Here's my exports file:

/storage/public *(rw,async,no_subtree_check,insecure)

Does someone know what could it be?