Just some random hints.
1) Is the right Brand for your heat pump selected?
2) What is the signal on your CTSmall? look at the SYS led just after power up?
3) If you remove the power from CTSmall and your number is in the alarm list, do you receive the alarm SMS?
4) When CTSmall receive a SMS the SYS led flash fast green?
5) When CTSmall is sending a SMS SYS led flash fast green? In case of problem it flash red!
6) Is the SIM pin code removed?
7) Try with another SIM card, or a SIM card from another provider.