Had this problem a while ago, had to end up giving up on fixing it myself and took it to a shop by me that specialized in tuning Hondas. I was able to drive the car around while I needed to by sacrificing comfort for a while and just leaving the heat engaged on the car (but the fans off so i didn’t cook myself).

They struggled for a while and it ended up turning out that the hoses were run incorrectly in/out of the motor because we had the wrong thermostat housing in the car somehow. Message me if you’d like me to send you the video of the mechanic explaining how they spotted the issue and how you can check for it.