Instead of trying different firmwares, maybe it would be more productive to try a wireshark capture of the PPPoE negotiation. For PPPoE to work,
- PPPoE server and client must be in the same broadcast domain
- Although optional, if configured in the PPPoE client, both Access Concentrator (AC) and Service Name must match between the PPPoE server and the client. Mikrotik uses the assigned router name as AC.
- Make sure user/password match in both client and server.
- If using a static IP address on the client side, the server must be configured to NOT assign an IP address to the client. If dynamic IP address is to be used on the client side, the server must be configured to assign an IP address to the client from a pre-configured pool of IP addresses.
- ePMP PPPoE client authentication ONLY supports PAP and CHAP.
You could also use the "tcpdump" functionality from the SM's CLI to do a capture.
I see a mismatch of Service Name (service1 vs temp) and AC (MikroTik vs Cambium). Can you remove those two fields from the SM PPPoE configuration (leave them blank) or make them match the settings in the router?
IP configuration should be ok the way you have it for just one client.