I've noticed that SMS messages weren't being sent and discovered that mmcli -L was yielding No modems were found . This is annoying. After checking through several online forums where folks reported similar disappearing modems, including one that turned out to be a hardware failure (hopefully not my problem!), I ran across a suggestion to change /usr/lib/udev/rules.d/80-modem-eg25.rules to replace {power/control}="auto" with {power/control}="on" and then issued a systemctl restart udev for good measure.
We'll see how it goes...
