You are running out of space on your device's hard drive.

OneDrive for Business files are taking up too much space on your system's hard drive. The files are stored in the cloud (i.e., Microsoft's servers) as well as your device.

One possible solution is to look through your files on the desktop application and set some files to only be stored on the cloud. You would likely only want to do this for files that you would not need to access offline or locally.

1) Navigate to your OneDrive for Business files in File Explorer or Finder.

2) Find files that are stored both on your computer and the cloud. These files will have a green circle with a white background and a green check mark to the right of the file name. This is called a green tick icon. Please see Microsoft's documentation at https://support.microsoft.com/en-us/office/what-do-the-onedrive-icons-mean-11143026-8000-44f8-aaa9-67c985aa49b3 for image examples.

3) Identify which files can be stored on the cloud only.

4) Right-click on one of these files and choose Free up space. The green tick icon should change to a blue cloud icon.

5) Repeat the previous step until all the files that need to be cloud-only are set to cloud-only.

OUTCOME

Files that were previously stored on your hard drive and the cloud are now cloud-only. This should free up some space on your hard drive.