I just installed Opera and imported my bookmarks. When I try to go to my gmail, I get the same message about cookies. I verified all the settings and still cannot access my gmail account. What am I missing?

I found a solution online. Use Control-Shift-Delete while in Opera to bring up a window to clear browsing data. Be sure Browsing History, Download History, Cookies and other Site Data, and finally Cached Images and Files are all checked. Then from the Dropdown, select The Beginnng of Time. Close and re-open Opera and you should be able to sign into your Google Account and then all Google sites will work.

That fixed it for me and I can now access my mail, calendar, photos, YouTube, etc.