Proximus Cloud was recently upgraded and your Cloud account was set to "read only".
To add documents, music, etc. to the Cloud, you must first upgrade to the new version. Do this before 07/12 to continue using the Cloud.
If you have used up all your storage space, you will no longer be able to upload files to the Cloud. However, you can still perform operations that have no impact on your storage space, such as downloading or sharing files.
Free up or buy extra storage space to add files again.
You can check how much storage space you still have:
You will see an overview of the used storage space: