Problem with Site to Site VPN Ipsec - Fortigate

[abachtold]

Hello,

I have an Fortigate 60B. The VPN is between two different companies, i have control only on the B side.  In the A side theres a Cisco, i don't know the model or specifications. 

Specifications of the VPN

Has an NAT in my end to take an IP from the VPN to foward for my server that wil use the connection. 

On the B site it uses the network 10.28.3.96/27, the server in that side uses the IP 10.28.3.100.

The tunnel goes UP in the monitor. The server in A site sends an telnet in the port that we will use in the application and via wireshark in my server I see the package here, but all tests and communications in my side does not reach even their firewall.

How can I troubleshoot this problem, I can send print of all the configurations and so. This can be a problem of my internet provider?