Hi Adam,
I would like to collect some more information to better understand your situation.
1.The browser you are using. Have you ever switched to another browser?
2.The detailed version of the OS X.
3.The operating system of your Mac Book Pro.
4.About “I cannot scroll in the online version of office 365”, could you provide a screenshot of your web interface?
To upload the screenshots, you can click Use rich formatting when replying and then click the Insert image button.
Thanks,
Alex