We are using Jira Cloud and have been for some time. Across numerous projects, suddenly today across numerous projects we are not able to pick up our epics and add tickets to epics via the Epic Link field.
Is this a known issue? Seems likely that this is a bug on Atlassian's side? 
This screenshot shows me searching for the epic "Frogworks" which is an epic within the project I am working in, but no results are being returned.
This is the issue we are seeing across multiple projects within our Jira instance. Note: if I am in the backlog view, I am able to drag a ticket onto an Epic via the Epics panel, but this is the ONLY way that we can add a ticket to an epic. For example, if the ticket is In Progress, it is not possible to add the epic to the ticket via the epic link field - I would have to move the ticket back to the backlog and drag it onto the epic that way!
Please help!