A few more comments in addition to what Steve has just explained.
The normally closed circuit is the problem. MOSFETs, whether P-channel or N-channel, require a gate-source voltage to be applied to them to make them conduct. The difference between them is just the polarity of that voltage; without applied voltage, neither type will conduct.
As Steve mentioned in an earlier post, depletion-mode MOSFETs do conduct by default, but they're not available with any significant power-handling capability.
So you cannot (at least, I don't know of any way to) make a drop-in replacement for an electromechanical relay that has two input connections and a normally closed output and nothing else. You need to get access to some kind of power source to provide bias to the MOSFETs in the normally closed path.
You can provide a power source at the input side, if input power is available, and transfer it to the MOSFETs for the normally closed path using the same method you are using for the normally open side. You would need a separate photovoltaic coupler, because (a) one needs to be energised when the other one isn't, and (b) the commoned sources of the MOSFETs in the NC and NO paths must be electrically separated. You would also need to arrange the input circuit so that the isolator for the NC circuit has a power source that's active when there is no voltage across the inputs that activate the isolator for the NO circuit.
In this case you could (and should) use N-channel MOSFETs for both paths.
Another alternative is to use voltage from the output side to activate the MOSFETs in the NC circuit. If the output is switching an AC circuit, it might work out better to use an SCR or triac. It will not conduct for the complete cycle, though. If you use an SCR or triac, you could control it with a simple optocoupler, which could be driven from the same inputs as the photovoltaic isolator; when the optocoupler is energised, it would short out the gate-cathode voltage for the SCR or triac and turn it OFF.
We could give you much more specific and helpful advice if you showed us how this relay replacement device will be used. In other words, a really COMPLETE circuit, including a description of the devices that need to connect on both sides of it.