AutoHotKey Not Working in Certain Applications?

[mcfarjac]

I have a script that essentially duplicates barcodes per below. It's not working on 1 specific inventory application called WorkflowRx on a windows 7 based computer with a generic log on.

It will work between 2 notepads on that computer.
If I start with notepad on that computer, and scan a barcode, it will alt+tab to WorkflowRx, but won't enter the barcode a second time.
If I remote into the server of the application from my laptop, the script works correctly.
We've tried different scanners...with and without {enter} after the barcode

I'm hoping someone might have some insight!

Script:
Loop 10
Hotkey, % "$~" A_Index-1, BarCodeHandler, on
BarCodeHandler:
Accu .= SubStr(A_ThisHotkey, 0)
If Strlen(Accu) > 8 && A_TimeSincePriorHotkey < 60
SetTimer, TheBigShebang, -60
If (A_TimeSincePriorHotkey > 100)
Accu := SubStr(A_ThisHotkey, 0)
return
TheBigShebang:
If Accu
SendInput, {Alt Down}
Sleep 2000
SendInput, {Tab}
Sleep, 300
SendInput, {Alt Up}
sleep, 100
SendInput, %Accu%
SendInput, {enter}
sleep, 300
SendInput, {Alt Down}
Sleep 100
SendInput, {Tab}
Sleep, 100
SendInput, {Alt Up}

return