Please see below a problem that i seem to be having. Some of these clients haven?t had readings for a while i was wondering if there was a software upgrade at all as my technician has gone to check sights and says the signal is perfect and everything is working. I have also checked airtime and they are all fine.  (cell phone numbers censored to protect customer)

No, it doesn't seem to be software upgrade related. If that was the case, chances are it would have affected all the meters at the same time, or a lot of meters, from the same date.
In your case, the dates when the problems started happening are all different for different meters.
Most of your problems are 'Could not connect'.
I believe all your modems are the KOCOS modem? To troubleshoot them, SMS NET to them. The modem should answer your SMS. Try it with a modem that does work, like 0796548860 to see how it should behave.
If you do not get an SMS reply, that means that the modem does not have power, or does not have signal, or there is a SIM card/contract/airtime problem.
If there are no LED's alight on the modem when installed on the meter, it does not have power.
To fix, check that the plug from the modem is in properly. Check that the meter itself has power.
The modem have a row of green LED's that gives an indication of the signal strength. Also, when the modem switches on the first time, there is a light that flashes long on, long off. When the modem connects to the network, this changes to flash short on, long off. When the modem logs in to GPRS, this changes to short on, short off, short on, long off (double flash).
Ways to possibly fix a bad signal is to: Check that the arial screw-in connection is tight;
Move the arial: To see if there should be signal, or where there is good signal, hold a cell phone of the same network right next to the meter/modem/arial, and see on your phone how good the signal really is. Check the signal indication on the modem to see if it really has signal.
To troubleshoot a SIM card problem, simply take the SIM card and put it in your phone. Send and receive SMS, and browse the internet. If you can do those two things, the SIM card is fine.
What we find is also very helpful sometimes when approaching problems like these, is to swop out components of a non-working site with working components. For example, swopping out the modem, or the SIM card. It could be that one of the components is broken.
For example Colcoccio CT did not reply when I smssed NET to it, but Ocean Basket Tyg did. Therefore, a power, signal, modem or SIM problem. And this fault was determined without any dependency on Plug and Play Scada whatsoever: just with my cell phone talking directly to that modem.