Partially Greyed out sheets when opened

[Dunk4Divin]

Hi All. I have an MS Office 365 Excel workbook which analyses data and provides charts to show results and "filterable" data. I have buttons for navigation from a dashboard. When I navigate to any sheet for the first time it has parts of the sheet greyed out. If I navigate to another sheet (which is also greyed out partially) and then back again it is shown in full. Seems to happen to most sheets when workbook is opened but once cleared by navigating away and back stay ok until the workbook is closed and re-opened. I would be most grateful for any ideas. Thanks