@joseph_1979 Thank you very much - yes problem now solved

@joseph_1979 Thank you for your prompt reply. Yes I'm on V8.15.6. I've tried with and without hardware decoding - is that what you mean by HW Acceleration? Still no blooming image !!!! Not sure I've found the WIN Client Menu - is that 'System Settings' "Hardware Decoding First" as if so I've tried it enabled and disabled.

I can see my 510a cameras on my iPad under IOS but not on my laptop under Win10. Both connect to my LAN via the same wifi hub. Under Win10 the cameras are there for configuration but the image is blank. However if I go to clear any privacy masks that may be set the image is there in that bit of the app !! Saving having deleted any (probably non existent) masks works but still the image is blank when viewing the camera.

Any suggestions gratefully received.