Sending, receiving, and organizing email in Outlook on the web for business
I get a lot of pop up to buy Microsoft 365 also but I refuse to pay a subscription. I believe you may have the same copy paste issue, only in Excel. For Outlook, I found that lock symbol that takes you where you need to go. It is located on the left side of the Url address bar where it says outlook.live/mail/0/. I clicked on it and a pop up window appears where you can turn on the clipboard. That does fix it in Outlook. I suspect the clipboard sharing switch got turned off on your Excel page as well and needs to be turned back on. Microsoft did something with its clipboard, probably an update, that has turned off many users clipboard sharing feature which also cuts off the right click paste option.