Why is my Huawei CUN-L02 asking for a SIM network unlock PIN?

punylittlehumanoid

Prominent
Jan 21, 2018
2
0
510
During a recent trip overseas my phone has lost all SIM functionality and keeps prompting me for this, seemingly at random (not just whenever I try to use SMS). I haven't tried to change carriers and the SIM card is undamaged and correctly inserted. I can't find information on this from my carrier's website, spark.co.nz, and all results on Google seem to address changing carriers. Would love some light shed on this.
 

punylittlehumanoid

Prominent
Jan 21, 2018
2
0
510
I took the phone in to an outlet of theirs to get it checked out; they gave me a spare SIM card to try with it and the phone worked fine.

I had been using the SIM card for years but had cut it down 13 months earlier to fit my current phone. Turns out it just died really, really slowly.