Hello,
For IPSec to work, one of the routers needs to be reachable. If your RUT951 or RUT200 has a public IP and both your devices have internet access, it should be possible to establish an IPSec channel between them.
First, make sure that you configure PPPoE and that you have internet access. You can configure PPPoE by editing WAN settings in Network -> Interfaces -> edit WAN. There, select PPPoE and set other required parameters, such as a username and password.
In case you have a PPPoE server, you can take a look at the following configuration example here.
Then, when you have internet connectivity and, assuming that one of the devices is reachable via their IP address (for example, using a public IP address), you can configure IPSec. You can find the IPSec configuration example here.
If the IPSec tunnel is still not established, please replicate the issue and generate a troubleshoot file. To replicate the issue, turn on the router and give it some time to attempt establishing a tunnel. Then, download a troubleshoot file from System -> Administration -> Troubleshoot and attach it by editing your question. Attached files are only visible to Teltonika moderators.
Kind Regards,
Andzej