Acrobat PDF Maker - not converting Excell files to pdf

Hi, 
I am having some issues with several users at my work place not able to convert Excell files that are saved as xlsx using Acrobat PDF Maker tool within Adobe Acrobat STD. This suddenly started happening. 
What happens is when the PDF Maker tool is used if the Excell files has multiple tabs or no tabs the Excell will not convert to PDF and the original excel file if it had tabs they will become hidden for some reason. 
It works fine when the file is converted to the old excel format xls then the PDF Maker creates the PDF and dose not hide the tabs. 
Are you able to please assist? 

Thanks, 
Zoran