You need a transforming command (such as stats, timechart, or top) to return search results in a data structure that supports both tables and chart visualizations. Remove the table from the end and change your search like this
eventtype=egress_* File_Type=*| stats sum(Detail_File_Size) as Data_converted by File_Type | eval Data_converted=case( Data_converted>=(1024*1024*1024*1024),round(Data_converted/(1024*1024*1024*1024),0)."TB", Data_converted>=(1024*1024*1024),round(Data_converted/(1024*1024*1024),0)."GB", Data_converted>=(1024*1024),round(Data_converted/(1024*1024),0)."MB", Data_converted>=1024,round(Data_converted/1024,0)."KB", 1=1,Data_converted."B")
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