I worked at duolingo each day during the last week, I scored more than 100 points on some of these days, and all of a sudden duolingo records 0 points for all these days for me. I deleted all my browsing history, cookies, etc. earlier today. Could that be it?
Shouldn't be. Duolingo stores the info on its server, not your computer. (Generally, people can log in from different computers/devices and find their work as they left it.)
Just to be sure, is there any chance you accidentally created a brand new account, instead of signing into your existing account?
Thank you for your comment. What happened is I was offered a placement test and was promoted to a new league. I worked for a few days from this new status and then, on the day I posted my message, I found myself back, to where I had left off, in my original league. The few days when I worked from the more advanced league were recorded with zero activity, although I had scored many XPs.
I understand now this was not caused by my deleting cookies, but rather by some Duolingo modus operandi. I do not believe I created a new account by accident.