Can't Progress to Next Level
I answer all the questions belonging to a level, and after the last question, the circle keeps going round and round, eventually ending in nothing. I keep retrying, but everytime, this is happening. Do something! I can't progress from one level to another!!
You need 17 more XP to reach the next level. Levels are not directly related to where you are on your tree but to the number of XP you have earned. It sounds as if you are finishing a lesson but it is having difficulty connecting to the internet to record this fact. Are you using an App or are you using the web interface? The app has a limited off line capability but will need a connection to synchronise your score. The web interface however needs an internet connection to work on a lesson.
Maybe your internetconnection is not good. Try your internetconnection with another application.
I have the same problem on my PC using with Google Chrome or Edge browsers - at the end of a lesson duolingo just shows the circling and when it eventually stops the lesson is still not completed and I lose the progress from that lesson. I have tried: clearing the cache, reopening the browser and rebooting but I still have the same issue. It works OK on my Android tablet, but I sometimes need to use the PC browser version.