In the original circuit (by @Andy-aka Open a circuit when voltage exceeds a certain value? ) , R2/R3/M2 are the first stage: when Vin*R2/(R2+R3) > M2.VThreshold, then M2 turns on. The second stage is M1/R1 where R1 keeps M1 gate on unless M2 pulls it high. Notice that Andy drew the original circuit with R2/R3/M2 together on the left, then M1/R1 on the right. In Andy's circuit, M2's gate drive does not depend on whether M1 is on.
Your circuit is similar to Andy's (with different reference designators, M1 and M2 swapped), and you replaced resistor divider R2/R3 with an adjustable trimpot R4. This is a great idea for prototyping, since it gives you some flexibility to adjust the circuit. I wouldn't want to use a trimpot on a production circuit unless there was no other choice, but for a prototype it's a good idea.
However, you connected R4 to the C1 side (the pass mosfet drain terminal) instead of the BR1+ power input side (the pass mosfet source terminal). So when the overvoltage detection mosfet M1 detects overvoltage condition and turns on, the pass mosfet M2 turns off, and that in turn turns off M1. You want M1 to stay on during overvoltage conditions. But since M2 gate depends on M1 and M1 gate depends on M2, it's unclear whether this circuit will reliably work.
A schematic is a 2-dimensional language, and there are a handful of ways that parts are used together. When reading a schematic, we look for commonly used expressions: op-amp with negative feedback, BJT in common-emitter configuration, a diode across the coil of a relay... and for MOSFETs, something must predictably drive the gate. Mosfets are often used with external resistor between Gate and Source, to ensure that V(gs) is zero if nothing is driving the circuit. Engineers try to help make their circuit schematics easier to understand by organizing them into these commonly used blocks.
I think what happened here was a minor transcription error turned a sensible circuit into something that doesn't work. R4 should connect to M1 source, so that it is powered by BR1+ regardless of the state of M2.