Onedrive full, cannot reconnect to Onenote files after logout

Hi Folks,

Been using Onenote on Samsung Galaxy for 6mths but did not realise Onedrive was full.  Logged out of Onenote but when logging back in my 6mths worth of notes cannot be found?  A brand new notebook is created?? Stumped as to where they have been stored, somewhere locally??? Any advice gratefully accepted. Thx Chris