Hi Mark,Wspr15 decoding is present only in wsprx version 08 as far as I know. The FST4W modes offered by newer wsjtx versions are different.
I use opera v1.6.5 set for 136 kHz and mode Op32, but older version work too. Unfortunately you can't enter an arbitrary tuning frequency; I suggest using 183.685 kHz, USB. That puts the signal right in the center of the opera tuning range of 1500 Hz audio. Unfortunately while Op32 is potentially quite sensitive it is also very prone to falsing. FST4W at rate 1800 seconds is much better in that regard. Perhaps some day I'll replace opera with it.
Wspr15 signals decode for audio between 1600 and 1625 Hz. So that I can run both codes simultaneously I set the RX BFO to 1390 in the advanced setup tab. Then the beacon is seen at +1610 Hz audio and the waterfall shows it at 185 (representing 185.185 kHz).
I also run ARGO centered at 1610 Hz. If the signal is strong enough to decode it should be evident on the ARGO waterfall at rate QRSS30.
Good luck and 73, Garry K3SIW EN52ta Elgin, IL