Ive never had home made yogurt fail from using the previous batch as the inoculum.
I have not used the IP but the principles are the same: live agents are added to warm milk, milk that has been denatured.
so : your inolucum did not have a live culture, the cultured milk was brought to to high a temp, thus killing the live culture.
if you got some 'curd' as you call it, and I take that to be an area of milk where culture did grow, then you did not add enough
live culture i.e. inoculum.
if you feel some culture was growing, mix up the batch carefully w a very clean mixing item and let it ferment for longer.
FD: I thought Id posted this a bit back
It seems to take more clicks sometimes than I realize
