Different network subnet server /client

hi all

I have configured ubuntu 18.4 urbackup server on 10.x.25.x/ 24 segment and client segment as 10.x.100.x /24 and all the define port are opened on firewall , but still my client are not reflecting on server. If reflect then after some time the client is showing offline… then after stop communicating and then nothing is happening.

Regard
Hitesh