@Johnnyjohn I think you will need to attenuate the gate from the 303 (iirc it is something like 10-14v) so it is probably saturating the gate input of the pyramid and so causing it to either stay open or closed, therefore not registering any notes. Either way it is a good idea to attenuate the gate as the pyramid is expecting 5v gates I believe.
The CV out of the 303 is within the range though, you can check the pyramid is receiving CV from the 303 by just connecting the CV (not gate) then go into settings/info then scroll to page 2 which will show the analog inputs and any activity on them. Obviously for the values to change the 303 will need to be playing.
Be aware that slides might not be captured correctly, I don’t think pyramid has a way of turning slides into midi pb messages, so slides will probably not sound right.
Hope that helps, I will test my 303 with the pyramid later and follow up/correct any of the above.
Edit: Also in settings/cv set cv in for CV not stereo or mono assign.