PPPoE connection disconnected again, and again

RouterOS General
1

We have an RB450G with RouterOS 5.7 on it, we use this device to share internet in a local network.
We have a LAN-net (so we got a UTP cable-end from the ISP), then we have to connecto by PPPoE to them.
It worked for a long time, but yesterday it dropped the connection.
We talked to the ISP, they told us nothing changed, and everything works on their side.
We changed the router to a TP-Link WR841N, and it works.

mikrotik does:
dialing…
disconnected
dialing…
disconnected
dialing…
disconnected
…and so on.

How can I debug, or know what is the problem?
Thanks for your help!

2

Hello torokp

At first i think you may try scan all active PPPoE servers in your network:
This is how I did it:

[admin@MikroTik] > /interface pppoe-client scan interface=ether2
SERVICE                                                               MAC-ADDRESS       AC-NAME
                                                                      00:90:1A:42:50:04 KV-JE-R1
                                                                      00:90:1A:42:61:C0 DP-JE-R2

If it not return any data, then problems with your connection to ISP. If else - perhaps problems with your configuration