I recently ran out of credit on my prepaid SIM and it took me a few days to get around topping up. Meanwhile, I lost the mobile data connection. When out of a known WiFi area, the network icon was grey with a star.

So far so good.

But when I topped up, I did not get my data back, only voice and text. For three days. Switching to offline mode and back did not help, nor did restarting network in Utilities or even a reboot. The only thing that helped was a power cycle. Only then did I get a SIM card PIN prompt again and, presumably, a new registration with my provider.

Is this a known issue? To be honest, the lack of the SIM PIN prompt after going offline and on again is unsettling enough (although observed on the N900 too, perhaps another Nokia leftover), no network recovery for days after the condition that caused losing it had disappeared is downright criminal.

I got this a while ago on EE (UK too). After running out of data, everything stopped working. Didn't realise data was out, assumed some network stack catastrophe so power cycled. Then after reboot all web traffic was being redirected to my account management page; I started a new weekly pack via text (more difficult/impossible via web), but then even after a wait and confirmation texts web traffic was still being redirected. Something somewhere was caching something or not re-registering. Ended up power cycling again too. Frustrating.

To be clear, I do not blame the provider (Three in my case), although I agree they could have handled it better. Your case was much worse.

I blame Sailfish for not providing any way of re-registering the SIM other than through a power cycle. My previous phone (running Palm OS) always asked for the SIM PIN every time I went offline and on again. It gave me the warm fuzzy feeling (maybe wrong, who knows) that offline really meant offline, with the GSM modem switched off.

I would expect that it depends on the quality of SFOS port and/or Android layer under it. For example, if you would be using OnePlus X with SFOS on it, it will ask you for PIN every time you get back from offline. /* you use the "official" device, right ? */

JP-1. As official as it gets.

It indeed sounds like there is missing use case scenario in the simcard handling.
Did you try killing ofono before powercycling?

I guess a reboot is at least as good as a kill (only power cycle helped)

killall ofono
How easy things may get (killall csd was not the way to restart phone/data functionality on N900). But I liked (and do like) the hard way...

And regarding PIN request on Jolla (C): neither offline mode nor ofono restart require you to enter it.
On N900 with the same SIM it was also not required. But with a dual SIM adapter (and switching) a PIN was required.

No, sorry, it did not occur to me. But, as Peter says, I would not expect a result much different from restarting network services in Utilities or rebooting.

I tried it now just for fun and, as expected, did not get a SIM PIN prompt.

Stupid question - I’m unaware of the processes surrounding prepaid SIM’s

Does the carrier have the ability to update or reset your balance, device and access at the SIM level? Do they even have to? Seems like running out of credit basically unregistered your device or something.

Keep us posted and forgive my dumb question. This is definitely a corner case that I wonder if Jolla ever had encountered before now.

At least when everything works well.
On all JP-01s in my household, when mobile data "went bad" (which is why I wrote the "nofono" restarter) ofono restart required re-entering the PIN. But a reboot will always restart ofono. Well, it's a reboot.

So my guess (as someone without a clue how this stuff actually works) is that at least part of this problem could be somewhere deep in the closed modem firmware which does not necessarily reboot with the "visible" OS.