Notes App stuck on Folders

I depend on the Notes App for storing important information and suddenly I find when I open the App the screen shows the word "Folders" but does not give any access to the notes or folders of notes that I have created. There is a search function but when I search for a folder that I know I have created, the search finds nothing. I can no longer access any of my notes. Tried turning off the phone & restarting - no change. Don't want to delete all and start again as I will lose valuable data. Looks like others have had this problem but the solutions I have read on help pages have not worked for me.