If you have Spotify installed on your iPhone/iPad, you may find that you are redirected to Spotify's application and then nothing happens when you attempt to sign into Pacemaker.
Spotify have confirmed this is an issue with their application which can be fixed by:
1. Opening the Spotify application.
2. Click "Your Library" at the bottom.
3. Click the settings cog at the top right.
4. In the menu, select "Social".
5. Ensure "Waze navigation" is set to ENABLED.
Now return to Pacemaker and attempt to login again. A future update to Spotify will resolve this issue.