When accessing /wp-admin a blank screen appears. The fix that worked for me was the following:
1. Backup current web files and database
2. Download a copy of WordPress from wordpress.com
3. Upload and overwrite website files with blank copy downloaded above
*NOTE – this will not overwrite your theme and settings
4. Refresh site and update database if required (prompted on screen)
I believe this issue was caused by an auto update of WordPress although not confirmed.