When we create a new workbook through File > New, we get a box where we can search for online templates. But, at times, it may be greyed out or disabled i.e. you can not type out anything out there.
To correct this, you need to enable internet setting for Excel.
File > Options (You can also invoke Excel options through shortcut ALT+T+O) > Trust Center > Trust Center Settings > Privacy Options > Allow Office to connect to Internet and Check this box.