Please help......Suspension issues

hi all. sorry not been on for a while but me and partner have been fighting with our 2005 Discovery 3 TDV6.
We have put it back on air suspension (it had been converted to coils before we got it but due to what it is being used for it needed to be on air) and we are, as you have guessed, having issues.
We converted it back and it was kind of working but had intermittent issues. Partner decided to replace compressor as it was very noisy and then he replaced seals in control valves. This sorted a lot of the issues but then all of a sudden the suspension stopped working completely and it is now sat on the stops.
We put a diagnostic on it and for some reason we can not communicate with the suspension ECU.
Has anyone else had this issue and if so any ideas of where we can start our search?

Thanks

I have very limited knowledge of the D3 compared to others however:-

1. Did you replace the relay?
2. Is the compressor plugs within the compressor housing plugged in? ( not come apart? )
3. Is the ECU damaged? i think it lives in one of the foot wells

I am sure @gstuart will be able to assist your suspension issues though

ECU is fine as far as we can tell. All relays have been checked and are working and compressor has been changed for a new one and all plugged in. Like i said it was working in a fashion with only the odd issue now and then but now its sat on the stops and not even the compressor is kicking in. We were at one point able to get into the suspension ECU but it would not allow us to calibrate the sensors but now we have nothing and nothing has been altered. Its like the ECU has just gone missing and cant be found

Following this with interest as my Disco 3 2005 has now got issues with the suspension
It is a tho the compressor is not working, as when you drive it, it is so springy and bounces along the road for the 200 yrds that I drove it before heading back home
any advice would be very much appreciated
Hope all well