Unable to authorize application to Box (invalid_client)

We have some users that are unable to authorize our application to use Box on some browsers, but not all users experience this problem (even with the same browser version). We've seen problems with both Firefox and Chrome.  Box complains of an invalid_client, but a valid client_id is consistently used.

The app is making this API call:

/oauth2/authorize?response_type=code&client_id=yzaosnsz05wyeintw4hpoi2ym8xf4o94&redirect_uri=https://cpm.it.umich.edu&state=&box_login=

The error from Box is:

Error: invalid_client

• scope=root_readwrite
• folder_id=
• response_type=code
• redirect_uri=https://cpm.it.umich.edu/authorized
• state=
• client_id=yzaosnsz05wyeintw4hpoi2ym8xf4o94