Hi, I've done a fresh install of 3CX Debian on a server this weekend, and rolled it out to 3 users. The system is working fine except on one PC (Windows 10) where the 3cx Windows Client throws a message: 3CX Phone for Windows could not establish a connection to the 3CX Phone System Web API. As a result, features like Contacts and presence information will not be available. You can still make and receive Phone Calls via SIP whilst we try and re-establish full functionality in the background. The other PCs are working fine. I've removed and reinstalled the 3cx client, made sure the firewall and antivirus aren't blocking it, and tried using another users profile on the 3cx client. I'm thinking that something remains in the registry perhaps once the client is un-installed - I have a feeling that maybe the PC is still linking to a test install I did of 3cx and it's looking for the presence from a bad URL or something. Has anyone experienced this and know of a way to fix it? To confirm, other PCs on the LAN work fine, and this PC can make/receive calls, just the contacts and presence stuff is broken.