Ssl certificate is untrusted ( app IOS and HA running into synology )

I am struggling with this for few days…I dont know when but since days ago i cant get into HA app. It says that my SSL Certificate is untrusted. I have done few things such delete and create a new one ( i am using Synology NAS with let’s encrypt. Despite of this , still not working. My router is configured with DMZ and it is my NAS who is in charge to control everything. I have checked that port 80 and 443 are opened too. Any other ideas? Thanks in advanced!

I have the same issue, it was fine before, but when I’m trying to setup new instance I got the issue