Filter and Drag Options Missing on Excel 365 Browser

[jbiehl]

I have a worksheet that has multiple users working in it. Last week. while working in the browser, the cursor wouldn't change from a plus sign when hovering over the filters at the top of each column, preventing filtering. We also couldn't drag down by clicking on the bottom right corner of a cell. We could still edit the document, but certain features were missing. All the features worked normally when it was opened in the desktop app.

It was giving an alert that someone else had the document opened (although they didn't). However, if it was locked for editing, wouldn't that have locked all editing?

Thanks in advance!