I’m afraid that I’ve never come across such an issue when (re)installing/updating WSE RemoteApp before.

WSE RemoteApp installs a system service onto your Essentials server named “WSE RemoteApp Provider Service” (WSERAProviderService), and based upon the error log that you’ve provided, it appears that the installer does not have sufficient privileges to start the service once it has installed it on the server.

Have you locked down your Essentials server (or more specifically the TrustedInstaller user account) in such a way that it cannot start services that logon as the Local System account? If so, then you’ll need to undo that in order to allow WSE RemoteApp’s installer permission to start the “WSERAProviderService” service under the Local System account.

Other than that, are you running WSE RemoteApp 2012 R2’s installer (i.e. WSERemoteApp2012R2.wssx or WSERemoteApp2012R2.exe) from one of your connected client PCs, or are you running it directly from the Essentials server itself? If you’re running it from a connected client PC, then try performing a standard Remote Desktop connection to your Essentials server, signing in as a local administrator (not a domain admin), and then executing the installer directly from the local administrator’s server desktop instead.

Lastly, have you tried completely uninstalling any existing WSE RemoteApp installation and installing the add-in from scratch again?

To uninstall any existing WSE RemoteApp installation:

Open the server Dashboard, go to the “APPLICATIONS” page, select (i.e. highlight) “WSE RemoteApp” in the list of installed add-ins, and then click on the “Remove the add-in” task and follow the prompts.

NOTE: If the “WSE RemoteApp” add-in isn’t listed in the list of installed add-ins, then you’ll need to do the following in order to uninstall it:

1) From a local administrator’s server desktop, open the Registry Editor (i.e. right-click on Start -> Run -> regedit.exe), and go to the following registry key branch:

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Uninstall

2) Look through the subkeys of that branch until you find the one that’s for WSE RemoteApp (i.e. the one that has a “DisplayName” value of “WSE RemoteApp 2012 R2”), and then double-click on its “NoRemove” entry and change it from a 1 to a 0.

3) Open the “Programs and Features” Control Panel applet (i.e. right-click on Start -> Control Panel -> Programs and Features), locate the “WSE RemoteApp 2012 R2 Windows Server Solutions Add-in” program in the list of installed programs, and then go ahead and uninstall it from there instead.