Hi,
If I suspend my laptop while my LTE modem is connected, the connection
does not come back after resume unless I restart ModemManager (i.e.,
"systemctl restart ModemManager" or similar).
If I ensure that the connection is disconnected before I suspend the
laptop, then everything works fine on resume.
I suspect that ModemManager does not properly detect the suspend, or
that it does not properly update its internal state when a suspend is
detected, causing it to not do the correct things on resume.