TREX error logs & portal system

Hi,

Few outside users in our landscape gets error for searching knowledge articles on HTTPS connection

1)where their erros will be logged at TREX system

2)general erros log files of TREX system

3)How to find the connected portal system with TREX..I am not sure about the connected portal system with TREX in the landscape

Need to resolve the issue soon

I will appreciate all your help and guidance

Thanks a ton