Starting yesterday, you may have noticed that you are unable to create a new linked work item or link to an existing work item from ‘Links’ tab of a work item. This is a known issue affecting a subset of users. A fix is being rolled out and should be deployed to affected scale units before 9/1/2017 4am UTC.
If you are running into this issue, you can use one of the 2 workarounds listed below to unblock yourself.
Workaround 1: If you are trying to create a new linked work item, you can use the work item form context menu
Workaround 2: From a query view, you can use the context menu against each work item, or use the linking options available on the ribbon.
Sincerely,
Sri Harsha