Important: this article applies only for accounts on 2013/2016 Exchange plan.

Users may be unable to upload files or screenshots into a Persistent Chat room and face on the following error:

Error in transfer

Error

Per Microsoft, this is an unsupported feature for external users. Due to instability of this feature, Smarsh Hosted Services will be gradually disabling the file upload functionality across all the Persistent Chat rooms.

Note: this will not affect the ability to send files via regular Skype for Business conversations/meetings.

For sharing files you may use:

Read the Microsoft Knowledge Base article on What is persistent chat in Skype for Business? for more information.