Spreadsheet working on PCs and Macbooks but not on iPads or iPad minis

Hi,

Our excel spread sheet can be edited etc on PCs and Macbooks but when we try to do it on our ipad mini - it can't be edited (the whole reason we've created the spread sheet was to be able to access/edit it on ipad minis). Is there a method of making the spread sheets work on ipads/ipad minis? it downloads as a read-only application and we can't find a way to enable editing. Any suggestions?

What application are you using to try to edit the worksheet?

The office excel app

Do all the users have a 365 subscription and is the workbook hosted?

The devices have a shared 365 subscription (but I thought you didn't need to subscribe to edit anyway) and I don't know enough about hosts to know which one we're using - could it be SharePoint or OneDrive?

Ok, so we have it working now but you can only edit the spreadsheets on the ipads/ipad minis when it's unprotected so we're worried someone might wipe formulas accidentally if they don't know what they're doing. Any ideas as to how to protect the file but still make it able to be edited?