SetDataCell only work on Origin=Forms where data on the Origin=Import member exist

Can you give this a try and check the Error Log?  This is to capture the before and after amount in the data cell you are trying to clear.  Paste this in to the IsBaseEntity and IsLocalCurrency IF THEN condition.

Dim before As Decimal = api.Data.GetDataCell("Cb#Main:C#Local:V#YTD:I#None:F#NoneE#" & MainPovEntity & ":S#" & MainPovScenario & ":A#AC410000:U1#None:U2#None:U3#" & UD3Name & ":U4#None:U5#Local_GAAP:U6#None:U7#None:U8#None:O#Forms").CellAmount

'SetDataCell Command here

Dim after As Decimal = api.Data.GetDataCell("Cb#Main:C#Local:V#YTD:I#None:F#NoneE#" & MainPovEntity & ":S#" & MainPovScenario & ":A#AC410000:U1#None:U2#None:U3#" & UD3Name & ":U4#None:U5#Local_GAAP:U6#None:U7#None:U8#None:O#Forms").CellAmount
BRapi.ErrorLog.LogMessage(si, "SetCell Before/After check: Et= " & MainPovEntity & ", BeforeAmt= " & before & ", AfterAmt= " & after)