Upon completing the diagnostic, I found the drain line is clogged, which was disabling the thermostat from receiving power for safety future. Clean out the drain line and made a proper treatment to make sure it’s clean from mildew. After I got the system up and running, I complete the pressure test and found that the pressure looks good but when I did the split test, which is my delta was 6°, I notified Customer about a common problems which will cause something like this, and we decided to let today go by and see if it has to do with the high humidity in the house. Repair amount was authorized and will be paid by invoice.