I have a problem as described in the title. After entering Insights for ArcGIS through ArcGIS Online my previously created workseets are not visible. And I cannot create new ones. I can only access the workbooks through 'Content' tab on ArcGIS Online account but they are read-only.
I have no idea what actually happened. It used to work without any problems before. Please see the screenshots below. The app is in Polish but I hope everyone gets the idea.
App view after logging in (Main page) - the worksheets visible are not mine:

One of the previously created Worksheets - 'Content' tab view:

After opening the worksheet above:
