Excel 2016 new sheets show no gridlines?
Solution 1:
This is very late, but for someone running into this issue in future I tried lots of different things to fix this without luck.
Eventually after an exhaustive search of the registry I found that deleting the HKEY_USERS\<Your SID>\Software\Microsoft\Office\16.0\Excel\Options key fixed it for Office 365 (v2008).
As always with the registry, back up the key first. You may lose any changes you've made to Excel options, but otherwise I haven't noticed any negative side effects.