The UCServer 64-bit cannot be started after an upgrade.
Incompatibility 32-bit Access Database Engine on 64-bit Microsoft Windows systems.
The problem usually occurs when a Microsoft Office 32-bit is installed on the system or is installed later.
If the UCServer is installed in 64-bit architecture, make sure that no 32-bit Access Database Engine driver is installed in the system.
Uninstall Microsoft Office in the 32-bit version and install it in the 64-bit version (if Microsoft Office is needed on the server at all).
Install 64-bit Access Database Engine manually
The 64-bit Access Database Engine installation file AccessDatabaseEngine_X64.msi is located in the Support Files subdirectory of the UCServer installation directory (normally C:\Program Files\estos\UCServer).