Hi Alejandra,
As Vicky has already indicated it would be useful to know what OS are you working on and where your project is saved.
Users most often encounter this type of problems on Windows when working with a cloud drive such as OneDrive. The authentication methods used in these systems don’t keep their knowledge of a user’s permissions up to date robustly so you can appear to lose write access to a location. Unfortunately this is something that even Microsoft don’t seem to be able to make to work reliably for their own software!
To work around the issue, we therefore recommend always keeping your project’s working copy (the .ccpn folder/directory) on a local drive if you are on Windows. Use the archive mechanism to keep timestamped backups that you can upload to your cloud drive in case of local data loss. Your raw data (spectra) don’t need to be stored locally since they are typically only read.
Best wishes,
Brian