Logging in with WordPress works only after two successful attempts

Logging in with WordPress on app.simplenote.com works only after two successful attempts in case User never used app.simplenote.com in the current browser, deleted cookies or using an incognito mode.

### Expected
Expected to be logged in after the first successful attempt.

### Observed
The same Login screen is presented after the first successful attempt.

### Reproduced
1. Either remove all cookies for app.simplenote.com or open an incognito window
2. Open app.simplenote.com
2. Use "Log in with WordPress.com", login and let Simplenote to use WordPress account (approve)
3. Observe that you're redirected to Login screen
4. Use "Log in with WordPress.com", login and let Simplenote to use WordPress account (approve)
5. You're now logged in and can work with notes

### Where did you see the bug
- System Make:
- System Model:
- OS: macOS
- OS version: Catalina
- Browser (if applicable): Safari and Chrome
- Browser version (if applicable):
- Simplenote app version:

Start by reproducing the flow at app.simplenote.com in an incognito window or with cookies removed, using the “Log in with WordPress.com” entry point. Trace why the first approved login returns to the Login screen, and verify that one successful approval logs the user in and allows access to notes.

Written by the indexing model from the issue text.