Not able to login to client

## Bug report form
### Steps to reproduce
1. I'm annotating on: https://scholarlykitchen.sspnet.org/2017/12/21/wakeup-call-looking-back-2017-factors-affecting-2018/?informz=1
2. Highlights were working fine, but when I tried to make an annotation the client opened but not the annotation box.
3. When I tried to log in, I briefly get a blank pop up window which then disappears. So no way to login.

### Expected behaviour
Tell us what should happen.
I should be able to log in.

### Actual behaviour
Tell us what happens instead.
Pop up briefly appears--blank--then disappears.

### Browser/system information
Tell us which browser, browser version, and operating system you were using when
you encountered this issue.
Firefox 57.0.1 (64-bit)

### Additional details

## Feature Request Form
### Problem you are trying to address with this feature

### Your solution

### Add tags - did you add labels?
If this a customer requested feature, make sure to add that label.

Start by reproducing the login failure at the reported article URL using Firefox 57.0.1 and observe the blank pop-up and annotation behavior. The issue names no repository files or tests, so first identify the client login entry point and relevant authentication tests. Done means the login pop-up remains usable and the annotation box opens for the reported workflow.

Written by the indexing model from the issue text.