Worked great once, now it wont open

Just bought $5 of time and need it to record a conference call and it wont open. Hit the icon app, it starts for 1 sec then kicks out to home screen. Double click on home bottom on iPhone it shows it open,try open it from there and same thing. Back to home screen.
Grrrr!!

What upppp! about Call Recorder - VoIP phone calls & recorder, v8.6.0