As part of protecting your sensitive data, OneDrive and Sharepoint will block certain file types from being shared with others if they detect sensitive content such as Social Security Numbers, Credit Card numbers or other data as detailed in Data Loss Prevention (DLP).
If this occurs, you will see a folder icon with a red and white circle next to the file you upload like the one below:
You will continue to be able to access the file however any users you are sharing the file with will not be able to see the file at all.
The workaround for this issue is to remove any sensitive information from the file and re-share it.
As with all automated systems, this detection may occasionally produce a false positive. Such occurrences should be rare - however when they occur the file may not be able to be shared until the data that is incorrectly flagged as sensitive is identified and removed or re-worded. Please contact the information Technology Helpdesk if you are encountering a sensitive data block and cannot identify the information in the file that is triggering the block.