If Excel Online is not working and you see errors Couldn't Open the Workbook, or Request Was Taking Too Long, then see this post for the fix.

Are you trying to open RBF files on Windows? We list some of the programs like Restrospect and online tools like JeDok to help you open such files.

Learn how to use a Microsoft 365 setting to choose whether to open files in the online or desktop app, giving you full control for each file.