One of the main reasons is that the file is too large. One thing to try is to open the file in different programs like a text-editor or a different data software. In text-editors, for example, you can open large CSV files to view the data from the sheet in plain-text format that you can then parse into your own spreadsheet and collate as needed.
If further assistance is required, submit a ticket to Punchh Support. (For help submitting a ticket, click here)