SELECT has invalid inputs error everytime

[kymera]

hii I have a search bar in which when I write the UID this formula should find the most recent value in the Date column of each sheet for the current BMC UID and return the sheet name and corresponding date. If it doesn't find any matching data, it will return "No data found". but appsheet continues to give me SELECT has invalid inputs error and I dont know what to do 

IFS(
ISNOTBLANK(MAX(SELECT('New drones'[Data], [BMC UID] = [_THISROW].[BMC UID]))), "New Drone",
ISNOTBLANK(MAX(SELECT('Indoor Release'[Data], [BMC UID] = [_THISROW].[BMC UID]))), "Indoor Release",
ISNOTBLANK(MAX(SELECT('Released at Field'[Data], [BMC UID] = [_THISROW].[BMC UID]))), "Released at Field",
ISNOTBLANK(MAX(SELECT('Quality Check'[Data], [BMC UID] = [_THISROW].[BMC UID]))), "Quality Check",
ISNOTBLANK(MAX(SELECT('Client Fleet'[Data], [BMC UID] = [_THISROW].[BMC UID]))), "Client Fleet",
ISNOTBLANK(MAX(SELECT('Drone Repaired'[Data], [BMC UID] = [_THISROW].[BMC UID]))), "Drone Repaired",
"Nessun dato trovato"
)

[Markus_Malessa]

For starters I would suggest removing the single quotation marks. I think that is why you are receiving the invalid inputs error. That needs to be done for each select.