UCCX only accepts certain type of .wav format for any prompt files that it can use. The file format should be
8.000kHz, 8 Bit, Mono 7 kb/sec
Now there are a lot lot of posts detailing how to convert into this format but most of these result in 64kbp sample size which will work with UCCX 8 and Unity (haven't tested myself) but doesn't work with UCCX 7. I tried to upload these prompts and my version of UCCX just rejected all these.
Here are some of post which detail this process which would work for UCCX8
However, to get these working for UCCX 7, I used the following method
2. Open the MP3 or other format file that you want to use as prompt
3. For Goldwave
Once you have opened the file thaty ou want to convert Click on File>Save As and select following
For Switch Sound Convertor
Once file is opened, selection following from the bottom of window after clicking on Encoder options and click convert
Both of the above methods will convert the files into format which you can load onto CCX and it will work.