Getting Winwarbler to work with IC-7610 in RTTY FSK mode

Floyd Sense

New IC-7610 here and the goal is to get it working with Winwarbler on FSK RTTY.  At this point, I have PTT working, but no FSK output when transmitting.
In the 7610, I have these settings:

USB Send = DTR
USB Keying)rtty) = RTS
In Commander, Port = 5, baud=115200,N,8,1
DTR=off, RTS=Flow

When I go to the PTT-Rcving panel on General tab of Commander config, the rig responds properly to TX and RX.  
The second com port for the 7610 is Com4.

In Winwarbler config, RTTY tab, FSK LSB is selected, mark offset is -2125, optimal offset is 2210 and FSK control is EXTFSK64 (this is a 64 bit win 10).  I open the EXTFSK window and select Com4, FSK Output - RTS, PTT output-DTR.

In MMTTY setup, PFF&FSK panel, port is set to EXTFSK64.
MMTTY TX Port panel, COM-TxD(FSK) is selected, and pressing USB port button, C is selected.

In MMTTY soundcard tab, USB audio codec selected for reception and one of the blank items selected for transmission.

I return to Winwarbler, in RTTY mode, and press the Start button.  The rig (in RTTY mode) goes to TX mode and the EXTFSK window shows LTRS being sent, but the monitor audio shows that no data is being sent.  If data keyed into Winwarbler input box, EXTFSK shows data being sent, but it isn't heard on the monitor.  Why is the FSK data not making it to Com4?

Could be something not set right in the 7610 menus, but the manual(s) don't show examples for FSK from an external program.  I've read through most of the 7610 RTTY posts here, with no luck.Help!

73, K8AC

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