Excel always opens spreadsheet in read-only mode

I had the same problem. I could see the attributes set as Read-Only under the preferences but couldn't change them. I completely closed out of excel on my mac and changed the name of the excel file. That seemed to have changed the Read-Only status of my file when I opened it next. Hope this helps.

You actually may have a hidden lock file in the same directory as the main file is stored (usually happens to me when I use an USB stick to copy Microsoft files from somebody else). To resolve

• Open Terminal
• cd to the directory containing the file
• ls -al FIRST-CHARACTERS-OF-NAME*

If there is a small file with the same name as the file which only opens read-only but a different suffix -> rm THAT-FILE.