RB750 Connected to internet and PPPOE Server is running and working fine Site A is 2Km away from Site B so i used UBNT pair to connect both sides
Site A RB750 and its LAN ip is 192.168.88.0/24, LAN is connected directly to Access Point and its ip is 172.16.1.254. and on Site B Rb3011 which is directly connected to UBNT Client and ip is 172.16.1.253 Issue is i am unable to dial pppoe dialer from Site B it says waiting for packets

Is the UBNT connected to the RB750 in the same bridge with the PPPoE server?

Rb750 working as pppoe server and server locate ip to client from pool which is 192.168.88.2-192.168.88.254 and ubnt ips are static ubnt sender ip is 172.16.1.254 and ubnt reciver ip is 172.16.1.253

Edit title of your first post to something other than "Urgent help required". Describing your problem. You may get more readers.

Did you try adding the ether port that the ubnt device is connected to the pppoe server bridge