[RTTY] MP issue

[Dick Wilson]

My 'old' MP has antenna relay issues. I plugged in a replacement MP.
I thought I got everything installed as on the old one.
Found no audio to MicroKeyer box on receive. Radio has plenty of
audio. After plugging & unplugging, found that I could decode if no
headset plugged in. Plug in headset...no decode.
I can transmit RTTY. Hesitate to mess with Com-ports as it seems to
be more or less OK.
Found nothing in Yaesu or MicroKeyer manual. I know I am probably
overlooking a relatively simple solution. Can someone give me a hint
on where to look, please?

TU & 73,

Dick K6LRN