Hi Ron,
I presume you have read this: APRS2SOTA Spot Server
Specifically the point about the optional feature - “Activating callsign” may be what you need to use, but it’s not exactly clear to me how you insert that.
Never having used this service, so it’s probably best to contact Stewart G0LGS.
But from my reading of the post, I think if space is a terminator what you’re sending looks correct, but as the comment field can have spaces in it validly, perhaps try with some separator characters if you can - comma semi-colon etc. Something like this
W4T/SU-001,14.000 OTHER:K1LIZ:TEST ignore
I wonder if the “activating callsign” call sign also has to be registered with Stewart so that the system recognises it as a call sign?
73 Ed.