Direct PPPoE client WAN issue

Dear All,

Hope you are doing well this is my first thread here and if the category of the topic is not right you may move it to the right one

Please understand the scenario

There are two network topologies first one was working fine when we shifted to 2nd one we got issues

1st Topology:

TP-Link Router(PPPOE dialed) behind Mikrotik and it is a WAN for Mikrotik
Mikrotik is connected with the router on static configuration and the WAN router itself is using PPoE to make wan connectivity
in this scenario all users in the LAN after the Mikrotik were working fine there are different devices as we are providing fiber connectivity to users so that a user has two devices one is ONU and then second is his/her wifi router
There are different brands connected in the LAN at the user side it is tp-link, Tenda, Vsol & HSGQ

so the first scenario was working fine with no issue

now in the 2nd Topology

we skipped the WAN router and directly dialed the PPoE id in Mikrotik for the WAN connectivity now what is happening that those users who have TP-Link routers after ONU(if ONU is working in bridge mode) are working fine but those who have different brands like Tenda or directly dialed local PPOE in ONU they are unable to use internet

what could be the reason behind this failure of 2nd scenario?

Extra info:
Users in the LAN also dialing PPOE to Mikrotik
Mikrotik using PPOE Client for the wan connectivity in 2nd topology


Thanks
Regards:
AFZ