USG FLEX 200.Access to Web interface troughth WAN2(P2)

bk1

Hello. I have USG Flex 200 with firmware V5.32(ABUI.0). 

WAN1(P2) -  main provider. 
WAN2(P3) -  reserved provider.

I can't get access to Web interface when I try connected via WAN2(P3) but via WAN1(P2) - OK.
I changed settings on WAN2(P3) and connected my main provider, disable firewall, but i still can't connected.
What am I doing wrong?

bk1

@PeterUK Yes, I did it (Nat 443), doesn't work.
Today I Captured traffic for interface WAN1 and WAN2. Then I understood that problem with routing and created policy route. It helped for me. 

PeterUK

Might it be that you have made a NAT rule for port 443 on P3 to a LAN device? or even NAT 1:1?

or could your reserved provider not allow port 443 inbound or any inbound connection?