This is to confirm that we have fixed the issue. I'm glad to hear it works for you now and you all are able to access your Hosts.
Unfortunately, there was an unexpected issue that has occurred during the server's routine maintenance. Fortunately, we were able to fix the issue as soon as we managed to identify the cause. We apologize for the inconvenience.
The reason we're asking about antivirus/firewall software is just to exclude the possibility - sometimes a/v software updates their databases (usually without notifying users) and might mistakenly start blocking our software or access to servers. Please understand that we're not saying it's their fault - we're simply trying to identify if the affected machines have anything in common.
In addition, please try connecting to your Hosts once again and see if you're able to connect the time or if the issue still persists. Please note that in some cases it might take up to a few minutes for the connection to restore and start working again.
One more thing - those of you who have machines with Linux or Mac OS available (or even mobile Viewer app installed on your smartphone) - could you please try connecting to the same Hosts that you can't connect using Viewer for Windows and confirm if the issue occurs when using Viewer for Mac or Linux as well?
I've just checked with our developers on the issue and they've let me know that our servers are up and running and there were no recent downtimes or other issues on our servers within at least the last 7 days.
Could you please let us know if you have any antivirus/firewall software installed on your Viewer machine?
Unfortunately, the MINI license allowing only up to 30 connections to be added to the address book is a known issue in Viewer for Mac/Linux which will be fixed in the nearest update. We apologize for the inconvenience.
Could you please also let us know what version of Remote Utilities do you use and if the custom installation package is signed with our signature (the "online" configuration method) or if it's your own signature? If it's the Windows Defender blocking the installation, then are you able to locate any entries in the Defender's log that mention Host and if there are any false positive detections? Here's how you can locate and check the Windows Defender event log.
Could you please clarify if you mean running Agent or installing Host? Please note that Agent is a no-install module for spontaneous support, i.e. it does not require installation or administrative privileges and can be run by a regular user.