Based on your calculated column, I understand that you want to get workdays between two date and time columns.
Per my test, you could get the total number of workdays or total hours of workdays. But displaying the calculated result as h:mm is not available.
For total number of workdays:
=IF(Completed<Issued,(((DATEDIF(Completed,Issued,"D")))-(FLOOR((DATEDIF(Completed,Issued,"D")+1)/7,1)*2)),(((DATEDIF(Issued,Completed,"D")+1))-(FLOOR((DATEDIF(Issued,Completed,"D")+1)/7,1)*2)))
For total hours of workdays:
=(IF(Completed<Issued,(((DATEDIF(Completed,Issued,"D")))-(FLOOR((DATEDIF(Completed,Issued,"D")+1)/7,1)*2)),(((DATEDIF(Issued,Completed,"D")+1))-(FLOOR((DATEDIF(Issued,Completed,"D")+1)/7,1)*2))))*24
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