Daikin Altherma LC fault. model:erhq014aav3

Long time no post!!! My Altherma has been working fine for the last eight years until last week. the house temperature had dropped and when I checked the control unit there was a LC error flashing on the panel. The outdoor unit is not kicking in at all. On checking various sites this seems to be an transmission issue between the main indoor unit and the outdoor. I have checked the wiring between the two and check for loose connections on the outdoor unit but haven't come across anything. The HAP light on the outdoor unit is flashing green and the H3P light is orange and staying on. When I turn off the outdoor unit and turn it back on again it makes a kind of a thumping noise for a few seconds and then stops. Any thoughts appreciated!

Is this an LT or HT Altherma?

LT Altherma

Possible malfunction of transmission between inverter and control board A1P or A2P. ook for poor connection. Take each connector off and then push back into place.