I had this same problem again right now. Not only was I unable to receive any SMS, I was not able to send SMS either! They completely stopped working.
I have been on crimson for a couple months now, and I just updated via Gnome Software a couple days ago, and it still wasn’t working.
I checked if there were any SMS stuck in delivering state in the modem/SIM with mmcli and yes, there were 12 messages stuck. I deleted them all with mmcli but still, SMS wasn’t working. Sending now worked, but receiving still didn’t work, and even stranger, the mmcli message list was empty, there were no messages stuck in delivering! I tried multiple times with different people and an automated 2FA code sending service, but I didn’t receive any of their SMS.
I then tried something: I went to Mobile Network settings and changed Network Mode to 2G Only. Immediately, I got all the messages that I was waiting for, that were probably queued at the carrier!
Now I think this won’t work if I try to use mobile data, as I need 4G for that (I haven’t tried data with 2G only yet, but if the modem stays on 2G, I expect data to be extremely slow/unusable, if it works at all). The problem is that there is no “2G/4G (2G preferred)” option in the list. There are only options that prefer the 3G or 4G networks and only have 2G as one of the possible options, but none that prefer 2G. If I try selecting “2G,3G,4G“ it gives me an error: “The given combination of allowed an…” (this is all that I see as the text is cut off and it’s not possible to expand it) and it doesn’t switch to it, it stays at the previous setting. If I switch back to “2G,3G,4G (preferred)“ like I had before, it switches to 4G immediately and I think it’s pretty definitive that SMS won’t work in 4G at least with my carrier.
So for now I’m on “2G only“ so at least SMS and calls will work, and if I want to use data, will have to switch to 4G temporarily, breaking SMS while I use data, and then have to remember to disable data and switch back to 2G to make SMS work again.
Oh and I found the issue that was causing audio to not work and to drop out in calls randomly, it was VoLTE! I disabled VoLTE with BM818tool and now call audio works 80-90% of the time! The remaining times it doesn’t work from the beginning from establishing the call in the direction from me to the other party, as if my mic was muted (but it isn’t), but hanging up and immediately redialing will fix that. At least audio doesn’t break in the middle of the call when the signal gets weak and I can walk around in the middle of the call!
This seems to point to the modem being the main culprit behind all these call and SMS issues. It could probably be fixed in the modem firmware, I know Purism had the ability to modify the firmware at some point in time, whether they had someone in-house or an external contract or even the modem OEM, but they haven’t released any new modem firmware for years now, so they probably don’t have that ability any more.
I have to say, I am extremely disappointed with Purism and hos they handled this issue. They know about call audio and SMS issues for more than 2 years now, and they shrugged them off. They treated their own product as abandonware, they didn’t even fix the basic features required for it to work as advertised, as a basic dumb cellphone! They left us to deal with it. Many users posted on this forum they were just gonna stop using the L5 completely and go back to Apple/iOS or Google/Android because ay least they work!