To be clear your not trying to have samples in the ren effected but the sp404.. You already have samples in the sp404 and want the ren to sequence the sp404?
If you use the word "sync" it means the sp404 also has a sequence, and when you start the ren, you want the sp404 to play it's own sequence/patterns along side the ren in sync..
I'm assuming you just want to trigger the sp404 samples via ren sequencer...
in preferences under the midi tab, make sure the midi out ports your using matches the settings... like this

when you plug in your sp make sure it's in out put port a...
also assuming that your sp audio out is plugged into the audio in off the ren.
make sure the track your using is set to midi and that it is using midi out port a...
like this
