Hi Neil, 

Welcome to Box Community and glad to help! 

You may want to check the following, 

• Did you succesfully uploaded the file on a shared folder? If not, make sure you've invited the user. 
  


• Did you confirm with your colleague if she/he's looking at the same exact folder where your files were uploaded? 


• Is the user currently accessing the folder in his/her local box folder or through box.com? Can you ask him/her to use the latter?

Hope it works!