RECentral 4 will not open and shows “lost system file ksxbar.ax” error message after Windows 10 has been updated with the April update version 1803, what to do?
RECentral 4 fails to start and shows following error message on computer with Windows 10 Spring update 
This error is resulted by the new Windows 1803-update that controls the way of applications connecting your webcams and video capture devices.
Please refer to following steps to resolve the situation:
In Windows Search type “Privacy Settings” then click “Enter”
At Privacy Settings/ App Permissions/ Camera find the toggle and make sure to set it on
“Allow apps to access your camera”
With this setting you can get your AVerMedia capture card detected by RECentral 4.