Hi Laj, could you please check if permission for writing to storage is given for SecNotes. When you first installed and started SecNotes, it would have asked you to give permissions to write to storage. If not given at that time or if revoked in between, you will need to add the permission again.
Please go to your phone Settings -> Apps. Find and click on SecNotes and then on Permissions. It should show Storage permission as allowed. E.g.
When debugging found an issue where new installs on Android 10 would show up this issue. Basically an api got deprecated in android 10. Have fixed and uploaded a new version (8.7). Please update to it if the problem exists still. If you don't see the update, please wait for some time. Play store takes some time to sync updates to all regions.