Avast Antivirus software may block DriveHQ WebDAV Drive Mapping Tool (DMT). Most antivirus software does not block DriveHQ apps, e.g. (Microsoft's) Windows Defender, Norton and McAfee, etc. Avast just started blocking DriveHQ DMT about a week ago. The problem might resolve automatically in a few days (or weeks dependent on Avast).
If you experience a strange problem with DriveHQ DMT, e.g. you cannot save a file in the cloud drive (and it worked fine before), then please check if you have any 3rd party antivirus software such as Avast.
(a) If your computer OS is Windows 10, you don't really need 3rd party antivirus software. Windows 10 already includes Windows Defender antivirus software and Windows Firewall. You can simply uninstall Avast (or disable it).
(b) If you must keep Avast, you can add DriveHQ WebDAV Drive Mapping Tool to Avast's "Allowed Apps" list. To do so, please follow the following steps:
(1) Launch Avast GUI and open the main menu. Click Settings:
(2) In the Settings window, click "Blocked & Allowed Apps".
(3) If you see any DriveHQ programs in the list of blocked apps, please remove them. Then click "+ ALLOW APP".
(4) In the "Add allowed app" windows, click "SELECT APP PATH".
(5) Navigate to the path as shown below. ( C:\Program Files(x86)\DriveHQ\WebDAV Drive Mapping\ ), then select both MapDrive.exe (the GUI app) and WebDAVProxyCoreSvc.exe (the local WebDAV cache service process).
Once the two EXEs are added to the list of allowed apps, Avast Antivirus will no longer block DriveHQ WebDAV Drive Mapping.