>Application wrotes to screen using ? commands
>
>

SYS(602 , 1 )
>MODIFY WINDOW screen FONT 'Arial',14
>_Screen.Themes = .F.
>hide menu _msysmenu
>ACTIVATE SCREEN
>clear
>
>do while .t.
>clear
>  ?'1 Option1'
>  ?'2 Option 2'
>  ?'.  Exit'
>  
>  wait 'Select ' to valik
>clear
>...
>

>
>
>If running under RDP after switching to local desktop and back to RDP meu disappears. Whole screen is blank.
>
>How to fix this so that menu is visible after switching back to application ? I tried SYS(602 , 1 ) and SYS(602 , 0 ) but this
>does not fix blank screen.

Most probable, IMO, is that the app is not responding to periodic querying by Windows, so it considers the app dead or crashed. Include a DOEVENTS FORCE somewhere, preferrably on a timer. In my experience, the timer's interval should be somewhat shorter than 5 seconds.

In my case it was the long conversion routines, which would repackage tens of thousands of records from an outside source into the SQL database, and the usual echoing of log on _screen and periodic wait window nowait aren't considered signs of activity, so I'd get the milk-over-app whitish display, and the app would be labeled as "not responding". It stopped when I added this in the same periodic check. Just didn't put the check on each 100 records, but rather on every 10 and if number of seconds since last Doevents was >4,56 (which is my guesstimate, not from any documentation).