Hi, My dad is having an issue where he opens an Excel spreadsheet (.xlsx) and Numbers immediately crashes before even showing the document. I used Excel to export an empty spreadsheet and sent it to him to test, but it still crashes. Uninstalling and re-installing allowed him to open one document, but every document after that causes the same crash. He's running the latest version of Sierra, and the latest version of Numbers. Naturally, he doesn't want to use Excel. The document opens in iCloud and Google Sheets just fine, but neither will export to a Numbers document. Any idea what the issue is and if it's possible to fix?