There are really two separate things going on here, so it’s worth splitting them.
The “not supported for auto PA” message is a known Creality Hi firmware quirk, not anything you did. The Motion Advance / auto pressure-advance option got exposed in a firmware update (around V1.1.0.65), but the Hi’s toolhead doesn’t have the sensor hardware to actually run it, so Creality Print never inserts the gcode and the printer throws that error at the start of the print. It’s safe to ignore: turn Motion Advance off in your print settings and the message goes away. It is not what’s causing your bad prints. If you want pressure advance dialed in, do it manually with a PA test tower instead.
The sudden under-extrusion and weird layer lines after ~350 hrs is a different issue. “Fine for ages, then bad out of the blue” almost always means a partial clog or a gradually worn nozzle. A partial clog is sneaky — the first layers can look okay, then flow chokes down and you get gaps and inconsistent lines. Worth doing, roughly in order:
- Cold pull (heat to ~200 °C, pull the filament and check the tip — clean cone vs. chewed/blobby end).
- Inspect or just replace the nozzle; brass wears, especially with cheap or abrasive filament.
- Pop the extruder cover and check the drive gear for ground-up filament dust packed into the teeth.
- Make sure the filament is dry — wet PLA extrudes inconsistently and pops.
- Re-check flow/E-steps and that filament diameter is set to 1.75 mm.
If a cold pull plus a fresh nozzle clears it up, that was it. If not, post a photo of the layer lines and the cold-pull tip and we can narrow it down further.