SMA 5000TL-20 Inverter problem

gpigeon Registered Users Posts: 34 ✭✭✭
I have had 2 of these inverters in service for about 14 years and they have performed quite well.
One now is showing an "ISOLATION RESISTANCE"... " CHECK GENERATOR" error, so is no longer exporting to the grid.
Any suggestions as to where to start looking for the problem? I have already checked for moisture in the 4 roof top isolation switches. No problems there.
Where to next???
Thanks in advance.