Hi Cal,
I had this same problem using my TH-F6A and my FT-70.? I created a document (
Setting the RX Level in HamVOIP Allstar.pdf)? which is in the Files section of this group that discusses this and presents a way to disable DTMF muting so that you can see the DTMF levels using the "simpleusb-tune-menu" application accessed from the HamVOIP Admin menu (Item 12).? Careful tweaking of the RX level worked for me.
Steve - N8AR