Helpless in Remote Desktop of D-link router

I use D-link router DIR-300,
And i am helpless in remote desktop

i have 2 computer in LAN and i tried to connect them in remote desktop

so, i changed computerA’s port number to 3390
refers in “regedit” >> “RDP-Tcp” >> “Port Number”

then, i forwarded router public port 3389 to ComputerB’s private port 3389

and i forwarded router public port 3390 to
ComputerA’s private port 3390

then i use Computer B to use remote desktop connect to computer A
(connect to [router’s ip]:3390)

however….it fail again and again

plz, plz someone help me